Precambrian Research 191 (2011) 58–77

Home , Andean foreland basins, Basement high, Grenville orogeny, Guiana Shield, Stenian

Contents lists available at SciVerse ScienceDirect

Precambrian Research

journa l homepage: www.elsevier.com/locate/precamres

The Putumayo Orogen of Amazonia and its implications for Rodinia

reconstructions: New U–Pb geochronological insights into the Proterozoic

tectonic evolution of northwestern South America

a,∗ a b c

Mauricio Ibanez-Mejia , Joaquin Ruiz , Victor A. Valencia , Agustin Cardona ,

a d

George E. Gehrels , Andres R. Mora

Department of Geosciences, The University of Arizona, Tucson, AZ, USA

School of Earth & Environmental Sciences, Washington State University, Pullman, WA, USA

Smithsonian Tropical Research Institute, Balboa-Ancon, Panama

Instituto Colombiano del Petroleo ICP, ECOPETROL, Piedecuesta, Santander, Colombia

a r t i c l e i n f o a b s t r a c t

Article history: Outcrops of late Meso- to early Neoproterozoic crust in northwestern South America are restricted to

Received 13 June 2011

isolated exposures of basement inliers within the northern Andes of Colombia, Peru and Venezuela. How-

Received in revised form 12 August 2011

ever, evidence for the existence of an autochthonous Stenian–Tonian belt in northern Amazonia that is

Accepted 13 September 2011

undisturbed by Andean orogenesis has not been recognized so far. Here we report ∼1200 new single-

Available online 17 September 2011

zircon U–Pb geochronological analyses from 19 Proterozoic rock samples of northwestern South America

collected from the Garzón and Las Minas Andean cordilleran inliers, drill-core samples from the foreland

Keywords:

basin basement, and outcrops of cratonic Amazonia in eastern Colombia (western Guyana shield). Our

South America

Amazonia new geochronological results document the existence of a previously unrecognized Meso- to Neoprotero-

zoic orogenic belt buried under the north Andean foreland basins, herein termed the Putumayo Orogen,

Putumayo Orogen

Rodinia which has implications for Proterozoic tectonic reconstructions of Amazonia during the assembly of the

Grenville supercontinent Rodinia. Based on the interpretations of new and pre-existing data, we propose a three-

U–Pb geochronology stage tectonometamorphic evolution for this orogenic segment characterized by: (1) development of a

pericratonic fringing-arc system outboard of Amazonia’s leading margin during Mesoproterozoic time

from ∼1.3 to 1.1 Ga, where the protoliths for metaigneous and metavolcanosedimentary units of the

Colombian and Mexican inliers would have originated in a commonly evolving Colombian–Oaxaquian

fringing-arc system; (2) amphibolite-grade metamorphism and migmatization between ca. 1.05 and

1.01 Ga by inferred amalgamation of these parautochtonous arc terranes onto the continental margin, and

(3) granulite-grade metamorphism at ∼0.99 Ga during continent–continent collision related to Rodinia

ﬁnal assembly. Along with additional paleogeographic constraints, this new geochronological framework

suggests that the ﬁnal metamorphic phase of the Putumayo Orogen was likely the result of collisional

interactions with the Sveconorwegian province of Baltica, in contrast to previously proposed models that

place this margin of Amazonia as the conjugate of the Grenville province of Laurentia.

1. Introduction Rodinia was assembled. In South America the Amazon Craton is the

largest of the Precambrian blocks that constitute the continental

Many reconstructions for the early Neoproterozoic platform (Tassinari and Macambira, 1999), and its role in the super-

supercontinent Rodinia predict interactions between a continent cycle has for long been recognized (Cordani et al., 2009).

Laurentia–Baltica–Amazonia triple joint along internal collisional Records of the participation of Amazonia in the supercontinent

orogens (e.g. Hoffman, 1991 or Li et al., 2008 for a recent review). Rodinia are expressed as: (a) metamorphosed passive-margin and

These different orogenic segments developed diachronously dur- rift sequences of the Sunsás-Aguapei and Nova Brasilandia belts in

ing late Mesoproterozoic to early Neoproterozoic times, and their western Brazil – eastern Bolivia (review by Teixeira et al., 2010),

timing deﬁnes the chronology for the collisional interactions that (b) scattered intracratonic magmatic events and shear-zones

took place between different crustal blocks and microcontinents as developed obliquely with respect to the colliding margin (review

by Cordani et al., 2010), and (c) paleomagnetic evidences obtained

from late Mesoproterozoic volcanic and sedimentary rocks of the

∗ Rondonia region in Brazil indicating proximity and interaction of

Corresponding author.

this margin of Amazonia with respect to (modern) SE Laurentia

E-mail address: [email protected] (M. Ibanez-Mejia).

M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77 59

(Tohver et al., 2002; D’Agrella-Filho et al., 2008). Although the with autochthonous Amazonia basement, improves our knowledge

involvement of Amazonia in Rodinia is in general a well-accepted about the evolution of the Proterozoic orogens of South America

hypothesis (e.g. Li et al., 2008), many details and questions and provides an additional piercing point in Amazonia for estab-

regarding intercratonic orogen correlations and the evolution of lishing intercratonic correlations with other late Meso- to early

Meso-Neoproterozoic collisional belts of the Amazon Craton are Neoproterozoic orogens worldwide.

far from being resolved. An example of this issue is the observation

that the Sunsás margin of Amazonia has been correlated by differ-

2. Geological setting – known provinces of the Amazon

ent authors with virtually every segment of the Grenville margin of

Craton

Laurentia (see Tohver et al., 2004a, and references therein), in part

due to the fact that the lack of geological and robust geochrono-

The Amazon Craton has been broadly subdivided in six different

logical information from northwestern South America has left its

Precambrian provinces (Fig. 1) and its evolution spans over 2 Ga of

role in many of these reconstructions mostly unconstrained.

Earth’s history. A detailed discussion about the general crustal con-

As a result of dense vegetation cover, heavy tropical weather-

ﬁguration of the Amazon Craton is beyond the scope of this paper

ing, and the development of Phanerozoic sedimentary basins, there

and only a brief summary of most relevant events are presented

are still sizable areas in northern South America where its Pre-

below. The interested reader is referred to the works of Teixeira

cambrian basement remains poorly studied or even completely

et al. (1989), Tassinari and Macambira (1999), Santos et al. (2000),

unknown. This is the case of the north Andean foreland basins,

Cordani and Teixeira (2007), and Santos et al. (2008) for a more in

where a large portion of northern Venezuela, eastern Colombia,

depth discussion on this subject. In general, it is thought that after

eastern Ecuador and eastern Peru (Fig. 1) comprise an area in excess

2 the amalgamation of Archean microcontinents along the Maroni-

of 800,000 km of covered basement. However, with the exception

Itacaiunas (MI) province during the Transamazonian orogeny, the

of K–Ar and Rb–Sr ages from wells presented by Kovach et al. (1976)

Ventuari-Tapajos (VT) and Rio Negro-Juruena (RNJ) belts evolved

and Feo-Codecido et al. (1984) nothing else is known about the

through the continuous accretion of intraoceanic arcs to this proto-

geochronology of this vast region.

Amazonia nucleus. The two marginal provinces located towards

Paleogeographic models that juxtapose the Sunsás margin of

the southwestern portion of the craton, the Rondonia-San Ignacio

Amazonia against southeastern Laurentia implicitly predict that the

(RSI) and the Sunsás-Aguapei (SA), are the result of accretionary

Meso-Neoproterozoic orogen of the Amazon Craton should extend

and collisional tectonics that took place throughout the Mesopro-

north of the Sunsás-Aguapei orogen, partly as a conjugate margin

terozoic (Sadowski and Bettencourt, 1996; Cordani and Teixeira,

to the Laurentian Grenville province under the Amazon River basin,

2007).

and possibly by interaction with a third continental mass even fur-

The RSI orogeny, which took place during the time interval from

ther north (e.g. Hoffman, 1991; Tohver et al., 2002, 2006; Fuck

ca. 1.56 to 1.30 Ga, is characterized by the accretion of early Meso-

et al., 2008; Li et al., 2008; Cardona et al., 2010). This interpreta-

proterozoic arc terranes overprinted by high-grade metamorphism

tion has beneﬁted from the occurrence of high-grade metamorphic

during the mid Mesoproterozoic by inferred collision of a micro-

inliers included within the north Andean orogen in Colombia such

continent – the Paragua block – against the RNJ continental margin

as the Garzón and Santa Marta massifs, among others (Restrepo-

(Bettencourt et al., 2010). Collision of the Paragua block against

Pace et al., 1997; Cordani et al., 2005; Ordonez-Carmona et al., 2006;

Amazonia resulted in high-grade metamorphism of the Chiqui-

Cardona et al., 2010). However, given the complex deformational

tania gneisses and the Lomas Manechis granulites at about 1.33 Ga

history of the northern Andes (Aleman and Ramos, 2000), in partic-

(Bettencourt et al., 2010; Santos et al., 2008), also coinciding with

ular its strong Meso-Cenozoic margin-parallel strike-slip transport

cessation of arc magmatism in the Pensamiento granitic complex

component (Bayona et al., 2006, 2010) and possible involvement

(Matos et al., 2009).

in later terrane collision event after the amalgamation of Pangea

Following the 1.33 Ga accretion event, a passive margin devel-

(Vinasco et al., 2006), the relationship between the cordilleran

oped in the area and a long-lasting period of tectonic quiescence

inliers and the non-exposed basement of the adjacent foreland

with localized intraplate extension followed, resulting in the depo-

basins remains uncertain.

sition of the Sunsás/Vibosi groups (Litherland and Bloomﬁeld,

The main objective of this paper is to present new zircon U–Pb

1981; Litherland et al., 1989) and the Nova Brasilândia aulacogen

geochronological results from Proterozoic basement rocks of north-

sedimentary sequences (Tohver et al., 2004b), respectively. These

western South America, in an attempt to clarify many of these

basins were later inverted and metamorphosed during the Sunsás

long-standing questions and provide a geochronological frame-

orogeny ca. 1.1 Ga (Teixeira et al., 2010), synchronous with defor-

work that can shed light on paleogeographic correlations involving

mation occurring along the Llano segment of the Grenville margin

the northwestern margin of the Amazon Craton. Samples reported

of Laurentia (Mosher et al., 2004). Collisional interactions affecting

in this contribution lie along a broadly NW–SE transect that covers

this portion of SW Amazonia during the late Mesoproterozoic have

most of the width of southern Colombia, ranging from exposures

been used as evidence for the participation of the Amazon Craton

of cratonic Amazonia (W Guyana shield), to samples from Pre-

during the amalgamation of Rodinia.

cambrian cordilleran inliers included within the Andean orogen

(Fig. 2). In addition to reﬁning the geochronology for various mag-

matic and metamorphic episodes in the north Andean cordilleran 3. The Proterozoic of NW South America

blocks and the western Guyana shield area, we present the ﬁrst zir- (Colombia–Venezuela–Peru–Ecuador)

con U–Pb ages obtained from basement drill-core samples of the

north Andean foreland basins as well as detrital zircon (DZ) analy- 3.1. Cratonic Amazonia

ses from high-grade metasedimentary units in the area. Our results

comprise the ﬁrst geochronological evidence for the existence of The northwestern-most outcrops of the Amazon Craton in

a previously unrecognized segment of an Ectasian to Tonian oro- South America are found in the Orinoco and Amazonas regions

genic belt underlying the modern foreland cover, herein termed of eastern Colombia, western Venezuela and northwestern Brazil

the Putumayo Orogen, which has a distinct geological evolution (Figs. 1 and 2). Most of the geological mapping in Colombia, along

with respect to its Amazonian analog the Sunsás-Aguapei orogen. with the only geochronological study available from this area,

As will be discussed below, recognition of this new belt provides a was conducted during the PRORADAM project (Galvis et al., 1979;

better cratonic reference for linking the Andean cordilleran inliers Proradam, 1979; Priem et al., 1982). The craton in this region

60 M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77

Fig. 1. Tectonic map of South America illustrating its major Precambrian constituent elements with emphasis on the provinces of the Amazon Carton. Modiﬁed from Cordani

et al. (2000) and Fuck et al. (2008). The location of the north Andean foreland basins is highlighted along with the location of drilling-wells from which core samples and

geochronological data have been obtained. (A) Area enclosing the known extent of late Meso- to early Neoproterozoic basement in the Northern Andes (fringing terranes).

(B) Autochthonous Putumayo Orogen underlying the Andean foreland. A possible northward extension into the Llanos basin remains hypothetical. Red dot: location of the

core samples presented in this study. Black dots: core samples presented by other authors; 1, Kovach et al. (1976); 2, de Souza Gorayeb et al. (2005); 3 and 4, Feo-Codecido

et al. (1984). (For interpretation of the references to color in this ﬁgure legend, the reader is referred to the web version of this article.)

consists of gneissic–migmatitic terranes of granitic composition 3.2. North Andean inliers

that yield Rb–Sr reference isochron ages of ca. 1.55 Ga (Priem et al.,

1982), and are intruded by undeformed granitoids with zircon U–Pb Along the Andean orogen, isolated inliers of Proterozoic gneisses

crystallization ages between ∼1.55 and 1.48 Ga (multigrain TIMS and granulites are known to be present in Colombia and have

by Priem et al., 1982). Some of these intrusives, like the Parguaza been the focus of intensive research (MacDonald and Hurley,

batholith of western Venezuela, display rapakivi textures and have 1969; Tschanz et al., 1974; Kroonenberg, 1982; Priem et al., 1989;

commonly been interpreted as anorogenic in nature (Gaudette Ramos, 2010; Restrepo-Pace et al., 1997; Ruiz et al., 1999; Ordonez-

et al., 1978). Carmona et al., 1999, 2002; Cordani et al., 2005; Cardona-Molina

Despite the lack of direct geochronological evidence, it has been et al., 2006; Cardona et al., 2010). However, as is evident in a recent

assumed that the Paleo- to early Mesoproterozoic provinces of the compilation of the available isotopic studies by Ordonez-Carmona

Amazon Craton extend beneath the north Andean foreland basins et al. (2006), precise geochronological data is still lacking for many

until they meet the Andes (Figs. 1 and 2), where they are thought of the exposed units.

to be truncated by “suspect terranes of Grenvillean-afﬁnity” Recent paleomagnetic data acquired in the Colombian and

accreted to the continental margin during proposed collisional Venezuelan Andes have shown the strong fragmentary character

interactions with Laurentia (Forero-Suarez, 1990; Gómez et al., of the pre-Mesozoic basement that underlies the Eastern and Cen-

2007; Kroonenberg, 1982, Restrepo-Pace et al., 1997). Rocks of tral Cordilleras of Colombia, the Santa Marta massif, and the Merida

apparent Paleoproterozoic age underlying these basins have only Andes and Perija Range of Venezuela (Bayona et al., 2006, 2010). It

been traced west as far as the location of the BT-1 well of was shown by these authors that different fault-bounded blocks in

PETROBRAS reported by de Souza Gorayeb et al. (2005); these the Cordillera, some of them associated with Proterozoic basement

206 207

authors obtained Pb/ Pb zircon-evaporation apparent ages inliers, have experienced signiﬁcant trench-parallel latitudinal

around 1720 Ma for a basement dacite in proximity to the transport of different magnitudes at least since Jurassic times. These

Colombia–Peru–Brazil triple border (approximate location shown data most likely preclude the idea of the “Garzón-Santa Marta

in Fig. 1). granulite belt” as a coherent Precambrian terrane constituting the

M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77 61

Fig. 2. Simpliﬁed geological map of our study area in south-central Colombia, showing the location of samples described in this study. (a) Major pre-Mesozoic features of

Colombian geology and location of the Putumayo and Llanos north Andean foreland basins. Modiﬁed after Gómez et al. (2007), (b) detailed map of the west Garzón and

Serrania de las Minas area in the Upper Magdalena Valley.

Modiﬁed from Gómez et al. (2007) and Jimenez Mejia et al. (2006).

basement of the Eastern Andes of Colombia (Kroonenberg, 1982; maﬁc granulites. This unit covers most of the massif’s western

Restrepo-Pace et al., 1997). Some of these blocks, as is the case of ﬂank and is in contact with the Las Margaritas migmatites along

the Santa Marta Massif, show displacements in excess of 1000 km the east-verging Las Hermosas reverse fault (Fig. 2b); (3) El Recreo

in magnitude with respect to a dynamic South America refer- gneiss, an orthogneissic unit of interpreted anatectic origin, and (4)

ence framework (see Fig. 7 in Bayona et al., 2010) while others, the Guapotón-Mancagua orthogneiss, a biotite-amphibole gneiss

like the Garzón massif, are considered to be relatively stable with of granitic composition that is exposed along the western mar-

respect to non-remobilized South America since at least the Paleo- gin of the massif and displays a foliation that is concordant with

zoic (Cardona et al., 2010; Toussaint, 1993). The cordilleran inliers that of the El Vergel granulites. The ﬁrst three units are also known

sampled during the present study, the Garzón, La Macarena and as the “Garzón Group” (Kroonenberg, 1982; Restrepo-Pace et al.,

Las Minas massifs, represent the southernmost inliers found in the 1997). Geochronological data for this massif comes from the works

Colombian Andes, located at approximately the same latitude as of Alvarez and Cordani (1980) and Priem et al. (1989), followed by

the wells we sampled from the Putumayo basin. Restrepo-Pace et al. (1997) and Cordani et al. (2005).

3.2.1. Garzón Massif 3.2.2. Serrania de la Macarena uplift

This basement inlier located in the southern portion of the The geology of the Macarena range (Fig. 2) was originally studied

Eastern Cordillera of Colombia (Figs. 1 and 2) constitutes the by Augusto Gansser (in Trumpy, 1943), who described its base-

largest exposure of Precambrian crust in the northern Andes. ment as an association of mica-schists and alkali-feldspar gneisses,

Based on regional mapping and mesoscopic characteristics of hornblende gneisses, amphibolites and deformed syenogranitic

the different metamorphic rocks, it has been informally sub- gneisses (Trumpy, 1943, p. 1282). Their Precambrian age was estab-

divided in four lithostratigraphic units shown in Fig. 2b and lished based on stratigraphic relations with the Güejar group, a

summarized by Jimenez Mejia et al. (2006): (1) Las Margaritas clastic sedimentary unit composed of micaceous and quartz-rich

migmatites, located along the eastern side of the massif domi- sandstones that rests unconformably on metamorphic basement

nated by metasedimentary gneisses and migmatites with mineral and contains trilobites determined as Cambro-Ordovician in age

assemblages indicative of amphibolite-grade metamorphic con- (Harrington and Kay, 1951) but no radiometric dates were available

ditions; (2) El Vergel granulites, a unit dominantly composed by for the crystalline rocks. Toussaint (1993) suggested that the base-

felsic granulites and garnetiferous paragneisses with subordinate ment of this sierra could potentially be correlated with the Garzón

62 M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77

massif as part of a larger crustal block accreted to Amazonia during following procedures similar to those presented by Johnston et al.

Precambrian times. (2009). Uranium and thorium concentrations are estimated using

an empirical intensity/concentration factor derived from the aver-

238 232

age U and Th intensities measured on our Sri Lanka zircon

3.2.3. Las Minas Massif

standard (average U of 518 ppm and Th of 68 ppm); the accuracy of

The Serrania de Las Minas is a NE-trending elongated range

our concentration determinations and derived U/Th ratios is bet-

of about 17 km in length and 6 km in width, located west of the

ter than 20% (Gehrels et al., 2008). Common lead corrections were

Garzón Massif (Fig. 2b). Structurally, this range sits along the axis 204

performed using measured Pb assuming a Stacey and Kramers

of a pop-up structure bounded on both sides by reverse faults that

(1975) model. The 202 mass was monitored in order to subtract Hg

thrust the Las Minas migmatites and gneisses onto Tertiary alluvial 204

isobaric interferences in the Pb peak using the natural ratio of

deposits to the east, and Jurassic volcanosedimentary sequences 202 204

Hg/ Hg = 4.34.

the west (Fig. 2b). The stratigraphic succession in this range com-

Final ages reported in the concordia plots, discussed through-

prises a high-grade metamorphic basement overlain by a clastic

out this paper, and summarized in Table 1, are concordia ages

sedimentary sequence of graptolite-bearing Ordovician shales and ®

calculated using the Isoplot Excel macro of Ludwig (2003)

sandstones of the El Higado Formation (Mojica et al., 1987). The

unless otherwise noted. Detailed concordia plots of the ca. 1.0 Ga

only geochronological result available for the metamorphic rocks is

metamorphic overgrowths are made available in supplementary

an hornblende Ar–Ar age obtained from an amphibolite (Restrepo-

material. Whenever a coherent cluster of concordant analyses is

Pace et al., 1997, sample HP-3) which deﬁnes a plateau cooling age

available for a group of zircons (or overgrowths) in a sample, the

of 911 ± 2 Ma, similar to other K–Ar and Ar–Ar cooling ages reported

concordia age arguably represents the best age estimate (Ludwig,

for the Garzón massif (Priem et al., 1989; Restrepo-Pace et al., 1997;

1998); ages given in the text and ﬁgures are quoted at a 2

Cordani et al., 2005).

conﬁdence level, and MSWD values reported represent those of

During this study we identiﬁed the metamorphic sequence as

combined equivalence + concordance (Ludwig, 1998). All analyti-

a series of stromatic metasedimentary migmatites overlying an

cal results are included in supplementary material and errors are

orthogneissic unit consisting of porphyroclastic augen-gneisses of

reported at ±1.

granitic composition. Most of the observed migmatites are stro-

For metasedimentary samples, analyses of inherited cores were

matic metatexites with apparent low degrees of partial melting,

carefully performed using the CL images in order to avoid areas

and the sedimentary origin of their protolith is evidenced by relict

of obvious metamorphic recrystallization. However, as will be evi-

sedimentary structures such as cross-bedding observed in psam-

dent from the concordia plots below, some of the core analyses

mitic layers that did not undergo anatexis. The foliated texture and

show departures from concordia either along a chord that goes

disposition of the granitic leucosomes, parallel to subparallel with

towards the age of the metamorphic overprint, affected by nor-

respect to the dominant metamorphic foliation in the host gneisses

mal (young) Pb-loss, or a mixture of both. Therefore, caution must

suggests that shearing and deformation were simultaneous with

be taken when interpreting one-dimensional probability density

the melting event (e.g. Kemp and Gray, 1999).

plots that consider only one isotopic ratio for the calculation of

the “preferred age”, as Pb-loss events at non-zero ages can gener-

4. Analytical methods: U/Pb zircon geochronology by ate artiﬁcial distribution peaks and lead to misinterpreting detrital

LA-MC-ICP-MS zircon signatures (as illustrated by Nemchin and Cawood, 2005).

For the probability density plot of each sample presented here (see

Zircon separates were obtained by standard methods combining Fig. 7), we took an approach similar to Collins et al. (2007) and plot-

jaw crushing, roller-mill pulverizing, water-table concentration, ted both the entire dataset of each sample (shaded in red), and the

magnetic separation using a Frantz LB-1 barrier separator, data ﬁltered at <5% discordance (black solid line). Although some of

and ﬁnal heavy-liquid separation using 3.32 g/cm methylene the smaller young peaks that are present in the plots of the entire

iodide. Approximately 100–150 individual grains were handpicked, dataset disappear when the data is ﬁltered (possibly generated by

mounted in epoxy, polished and imaged by SEM cathodolumi- mixing, recrystallization or Pb-loss), the position of the dominant

nescence (CL) both prior and after the analysis. Zircon textures peaks and their age maxima do not show any signiﬁcant variation,

description follow the nomenclatures presented by Corfu et al. which gives us further conﬁdence in the robustness of the obtained

(2003) and Hoskin and Black (2000). Interested readers are encour- detrital zircon data.

aged to download the high-resolution, color-cathodoluminescence

images that are included in the supplementary material, where the

5. Samples description and geochronological results

different recrystallization textures and ablation-pit mixing com-

plexities discussed throughout the text are exempliﬁed.

For the present study we analyzed samples of (a) gneisses, gran-

All U–Th/Pb isotopic measurements were performed by LA-

ulites and migmatites collected from three cordilleran inliers of the

MC-ICP-MS at the Laserchron center facilities in the University of

Northern Andes (the Garzón, Las Minas and Macarena massifs); (b)

Arizona following the procedure outlined by Gehrels et al. (2008)

drilling-core samples of deep exploratory wells that pierced the

using a GV-Instruments Isoprobe MC-ICP-MS, or a slightly modi-

crystalline basement of the Putumayo foreland basin of Colombia,

ﬁed procedure adopted for a Nu-instruments HR-MC-ICP-MS. Both

east of the frontal thrust systems of the northern Andes, and

spectrometers are coupled to Excimer laser systems operating at a

wavelength of 193 nm, and both have multicollector blocks capa-

238 232 208 207 northwesternmost cratonic exposures in the Amazonas region of

ble of simultaneously measuring U, Th, Pb, Pb, and

206 204 Colombia. Sample locations and other geographic names refer-

Pb isotopes in faraday cups while Pb is always measured

® enced in the text are shown in Figs. 1 and 2. Mineral abbreviations

in a channeltron detector or an ion-multiplier. This conﬁgura-

are after Whitney and Evans (2010).

tion was applied for analyses performed using ablation spot-sizes

␮

between 40 m and 22 ␮m in diameter whereas, in very small and

␮

complexly zoned zircons, we utilized 10 m or 18 ␮m laser spot- 5.1. Cordilleran inliers

sizes. For the small spot-size analyses masses 208, 207, 206 and

204 were all measured on ion-multipliers in order to allow reli- Seven samples collected in three of the basement inliers were

able measurement of the Pb isotopes with low ablation volumes, analyzed (Fig. 2), three of them from the Garzón massif (MIVS-11,

M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77 63

Table 1

Summary of the new U–Pb geochronological data presented in this article.

Sample Unit/location Coordinates Rock type Event Age ± 2 (Ma)

Cordilleran Inliers – Northern Andes

◦ ◦

MIVS-11 Garzón group N2 09 33.4 W75 35 37.0 Felsic granulite met 992 ± 05

maxdep 1115 ± 04

◦ ◦

MIVS-26 Guapotón gneiss N2 03 19.2 W75 42 47.6 Augen-gneiss met 990 ± 08

(Garzón massif) ign 1135 ± 06

◦ ◦

CB-002 Garzón group N2 07 37.7 W75 37 41.9 Metased gneiss met 992 ± 08

max dep 1016 05

◦ ◦

MACARENA-2 Macarena gneisses N3 01 45.0 W73 52 13.5 Felsic mylonite ign 1461 ± 10

◦ ◦

MIVS-41 Minas augen-gneiss N2 13 34.0 W75 50 30.3 Augen-gneiss met 990 ± 07

ign 1325 ± 05

◦ ◦

CB-006 Zancudo migmatites N2 13 26.5 W75 50 22.0 Maﬁc gneiss met 972 ± 12

(Las Minas massif) max dep 1088 ± 24

◦ ◦

MIVS-37A Pital migmatites N2 15 37.3 W75 49 49.9 Felsic gneiss max dep 1005 23

(Las Minas massif)

Exploratory wells – Putumayo Basin

◦ ◦

PAYARA-1 Putumayo N2 07 31.3 W74 33 35.9 Migmatite met 986 ± 17

Putumayo ign 1606 ± 06

◦ ◦

SOLITA-1 Putumayo N0 52 28.6 W75 37 21.3 Metased migmatite met 1046 ± 23

◦ ◦

MANDUR-2 Putumayo N0 55 24.5 W75 52 34.1 Amphibolite met 1019 ± 08

Putumayo ign 1592 ± 08

Putumayo Syenogranite ign 1017 ± 04

◦ ◦ ±

CAIMAN-3 Putumayo N0 45 13.6 W76 09 45.4 Metased diatexite met 989 11

Putumayo maxdep 1444 ± 15

Putumayo Leucogranite ign 952 ± 19

Cratonic exposures – Caqueta and Vaupes regions

◦ ◦

PR-3215 Araracuara S0 10 23.8 W72 17 24.2 Syenogranite ign 1756 ± 08

◦ ◦

J-263 Araracuara S0 40 20.7 W72 05 13.7 Syenogranite ign 1732 ± 17

◦ ◦

AH-1216 Vaupes N0 59 31.9 W69 54 24.6 Monzogranite ign 1574 ± 10

◦ ◦

PR-3092 Apaporis S0 19 08.1 W70 39 02.6 Syenogranite ign 1578 ± 27

◦ ◦

AH-1419 Apaporis S0 34 45.5 W70 15 26.1 Monzogranite ign 1530 ± 21

◦ ◦

CJR-19 Apaporis S1 01 10.3 W69 45 11.6 Syenogranite ign 1593 ± 06

Note: ages reported in this table are concordia ages unless otherwise noted (except DZ maxdep, see text for details). For every sample/population, 206Pb/207Pb weighted

mean ages are always in agreement with the concordia ages, but uncertainties are increased by about a 0.5–1% factor.

MIVS-26 and CB-002), three from Las Minas massif (MIVS-37a and distribution dominated exclusively by Mesoproterozoic grains,

MIVS-41 and CB-006), and one from the Serrania de la Macarena with the most prominent maxima at ca. 1120, 1300, 1370 and

range (Macarena-2). 1450 Ma. A maximum age of deposition for the protolith can be

estimated by the two youngest, >95% concordant grains of the

5.1.1. Garzón Massif detrital population. Two concordant to nearly concordant grains,

± ±

Three samples were analyzed from the western ﬂank of the with ages of 1115 4 and 1118 20 Ma and whose error ellipses

Garzón massif (Fig. 2b): MIVS-11 and CB-002 were collected from do not overlap with the age of metamorphism (supplementary

the El Vergel granulites unit and they correspond to a melanocratic data), place a limit for the age of sedimentation that is constrained

granulite and a banded leucocratic gneiss, respectively; MIVS-26 is between the age of the youngest detrital grain (1115 4 Ma), and

a coarse-grained granitic augen-gneiss collected from the Guapo- the age of metamorphism (992 5 Ma).

◦ ◦

ton orthogneiss unit. Sample CB-002 (N2 07 37.7 W75 37 41.9 ) is a sillimanite-

◦ ◦

Sample MIVS-11 (N2 09 33.4 W75 35 37.0 ) is a Hyp-Kfs-Pl-Qz bearing Qz-Fsp gneiss with biotite as the only ferromagnesian

felsic granulite with Hbl reaction rims around Opx as a result of phase, also interpreted to be of metasedimentary origin. Zircons

amphibolite-grade retrograde overprint. Zircons recovered from from this sample are mostly uncolored, but relatively more pris-

this sample were mostly rounded to subrounded in shape, colorless matic than those of sample MIVS-11 displaying width:length ratios

to light pink, with 1:1 to 1:3 width:length ratios and generally from 1:3 to 1:5. CL imaging shows a wide variety of internal grain

smaller than 200 ␮m in size. CL imaging shows that most of them morphologies similar to sample MIVS-11, although elongated

exhibit textures indicative of growth and/or recrystallization zircons with igneous zoning are more abundant. This sample

under metamorphic conditions (Fig. 3a, supplementary CL ﬁles) shows evidence of extensive solid-state recrystallization of inher-

evidenced by relatively homogeneous grains displaying only weak ited zircon cores by the granulite-grade metamorphic overprint,

sector-zonation or rims with no internal structure that appear as observed as widespread “ghost” oscillatory zoning patches in

overgrowths around more complexly zoned cores. U–Pb isotopic recrystallized portions of zircon grains and the presence of recrys-

analyses of the metamorphic overgrowths are all concordant tallization fronts (e.g. Hoskin and Black, 2000, supplementary

(Fig. 3a), and yield an age of 992 ± 5 Ma (MSWD = 0.32, n = 27) CL ﬁle). This feature is also evident in the U–Pb systematics,

interpreted as the timing of peak granulite-grade metamorphism where many analyses obtained from these recrystallized areas are

for this unit. Many of the grains contain xenocrystic cores, some of discordant and older than the age of metamorphism (Fig. 3b). The

which are characterized by oscillatory zoning typical of magmatic analysis of nine metamorphic overgrowths and individual crystals

zircons while others exhibit complex chaotic zoning patterns. The that display homogenous, bright and unzoned textures under

wide range of ages obtained for these xenocrysts, ranging from CL, are all concordant and consistent with an age of 992 8 Ma

ca. 1011 to 1490 Ma, reﬂects the detrital nature of these grains (MSWD = 0.3, n = 9) for the metamorphism, indistinguishable from

inherited from a possible volcanosedimentary protolith. A total the metamorphic age obtained for sample MIVS-11 described

of 89 detrital core analyses were performed, 62 of which are <5% above. A more cautious approach was taken for the analysis of the

discordant. The pattern is characterized by a multi-modal age peak detrital component of this sample given the strong metamorphic

64 M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77

Fig. 3. U–Pb concordia diagrams for samples analyzed from the Garzón and Las Minas cordilleran inliers.

overprint observed in the zircon xenocrysts; analytical spots introduced by recrystallization. All analytical data, including those

where carefully selected away from areas where recrystallization excluded from plotting, are reported in the repository data. The

is evident and placed in cores where original zoning is better detrital age spectrum for this sample shows a multi-modal age

preserved. Additionally, results plotted in the probability plot peak distribution of early Mesoproterozoic components similar

shown in Fig. 8 were ﬁltered to discard xenocryst grains whose to sample MIVS-11, with peak modes at ca. 1340, 1420, 1450

206 207

calculated Pb/ Pb age overlap within analytical error with the and 1480 Ma (Fig. 7). Even after ﬁltering the data as described

age of metamorphism in an attempt to reduce some of the “noise” above, there is a group of 11 inherited crystals whose ages cluster

M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77 65

around 1016 ± 5 Ma (weighted mean age). This gives us conﬁdence shows that most of the grains have xenocrystic cores surrounded

to constrain the age of deposition for the sedimentary protolith by bright, unzoned overgrowths presumably developed during

between 1016 ± 5 Ma and the age of metamorphism at 992 ± 8 Ma. metamorphism. Analyses performed on the metamorphic over-

◦ ◦

Sample MIVS-26 (N2 03 19.2 W75 42 47.6 ) was collected in growths yield an age of 972 ± 12 Ma (MSWD = 0.14, n = 7) for the

a small quarry close to the Guapotón municipality (Fig. 2b). It high-grade event (Fig. 3e). Interestingly in this sample, most of

corresponds to an augen orthogneiss with centimetric Kfs por- the xenocrysts are characterized by sector-zoning textures that

phyroclasts in a matrix of ﬁner-grained and oriented Hbl-Bt-Pl-Qz are suggestive of growth under metamorphic conditions (inset

that deﬁne the metamorphic foliation. Zircons from this sam- Fig. 3e), and have low-U concentrations typically between 70 and

ple are mostly uncolored, ranging in size from ∼150 to 300 ␮m, 250 ppm (see supplementary data). This observation contrasts with

with width:length ratios of 1:2 to 1:3. CL imaging showed all the other metasedimentary samples presented in this study,

that they consist of oscillatory-zoned igneous cores rimmed by where most of the xenocrystic cores display textures indicative of

more homogeneous, unzoned, metamorphic overgrowths (Fig. 3c, igneous crystallization. The probability function age plot for the

supplementary CL ﬁle). Concordant U–Pb analyses from the igneous detrital component is dominated by a restricted population within

cores yield an age of 1135 ± 6 Ma (Fig. 3c) that is interpreted as rep- the range from 1100 to 1200 Ma (Fig. 8), with a few restricted

resenting the time of crystallization for the igneous protolith. This grains falling outside this range. These outlier grains all show

age is within error of the SHRIMP age of 1158 ± 22 Ma reported igneous zoning textures and are also low in uranium. The 10

by Cordani et al. (2005) for this same unit. Analyses performed youngest grains of the detrital component cluster around an age

206 207

± ±

on the rims result in an age of 990 8 Ma (MSWD = 1.15, n = 15) of 1088 24 Ma ( Pb/ Pb weighted mean; MSWD = 0.21), and

that we interpret as reﬂecting the timing of peak metamorphism of constrain the maximum timing of deposition for the sedimentary

this metagranite, synchronous with granulitization of the El Vergel protolith between this age and metamorphism at 972 ± 12 Ma.

◦ ◦

unit (obtained from samples MIVS-11 and CB-002) and slightly Sample MIVS-37a (N2 15 37.3 W75 49 49.9 ) was collected

younger but more precise (although within error) with respect to from the northwestern termination of the Las Minas massif meta-

the 1000 ± 25 Ma SHRIMP age reported by Cordani et al. (2005). morphic core. It consists of a leucocratic, Qz-Fsp migmatitic gneiss

with biotite (extensively retrograded to chlorite) as the only ferro-

5.1.2. Las Minas Massif magnesian metamorphic phase. The outcrop is crosscut by a series

Three samples were analyzed from the Minas massif: MIVS- of slightly folded maﬁc dikes of unknown age. The analyzed sam-

41, collected from the granitic augen-gneiss that forms the core ple is interpreted to be a paleosome of these migmatites with some

of the range and the exposed metamorphic rocks; CB-006, a Bt- thin crosscutting leucocratic veins. CL imaging showed that most

rich melanosome from a metasedimentary migmatite in proximity of the grains have igneous growth-zoning patterns and resorption

to the orthogneissic unit; and MIVS-37a collected from an outcrop textures, but lack evident metamorphic overgrowths or extensive

of metasedimentary Qz-Fsp migmatitic gneisses on the northern recrystallization. U–Pb analyses conﬁrm that the analyzed grains

termination of the range (Fig. 2b). are detrital in character and that zircon did not grow or recrys-

◦ ◦

Sample MIVS-41 (N2 13 34.0 W75 50 30.3 ) is a Hbl-Bt-Mc-Pl- tallize during the metamorphic event but, instead, was probably

Qz augen-gneiss that forms the core of the massif and is well resorbed during anatexis. The entire age spectra obtained ranges

exposed along the Zancudo creek that drains the eastern portion of from 1005 ± 23 Ma to 1516 ± 21 Ma, and the dominant peak of

the range. Along this creek, outcrops of granitic gneiss are appar- the distribution has a maximum at ca. 1490 Ma. Grains that fall

ently overlain by metasedimentary migmatites but the contact out of this range constitute small subsidiary peaks at ∼1160 and

∼

between the two units was not observed. Zircons from this sample 1210 Ma. The youngest grain found in this sample is 2.3% dis-

are light pink in color, have width:length ratios between 1:3 and cordant and, overlapping concordia within analytical error, has

␮ 206 207

1:4, and reach up to 400 m in length. Internal grain structures a Pb/ Pb calculated age of 1005 ± 23 Ma. Although inferring

are characterized by igneous oscillatory-zoning, which in some maximum depositional ages from the youngest single-crystal anal-

grains is affected by partial recrystallization interpreted as a result ysis of a DZ distribution is a meaningful approach in most cases

of amphibolite-grade metamorphism (Fig. 3d, supplementary CL (Dickinson and Gehrels, 2009), the possible complexities in the

ﬁle). U–Pb analyses performed on the igneous cores reveal a mid- U–Pb systematics introduced by metamorphism could also imply

Mesoproterozoic age for the magmatic precursor of the gneiss, that this young age might well be an artifact of partial age reset-

calculated at 1325 5 Ma (MSWD = 0.96, n = 23). There is a subset ting of an older core during the ca. 990 Ma metamorphic event. We

of analyses that, although <5% discordant, clearly deﬁne a discor- adopt a maximum depositional age of ca. 1005 Ma for the protolith

dia mixing chord between the age of the igneous precursor and of these gneisses because (1) it could be a geologically reasonable

a younger age component. Using the small-spot ion-counter con- scenario and (2) is in agreement with results obtained for other

ﬁguration (12 ␮m) we were able to obtain a group of concordant metasedimentary samples presented in this study, but emphasize

analyses from thin, unzoned, brighter metamorphic overgrowths, that additional work needs to be done on this unit in order to obtain

which yield a value of 990 ± 7 Ma (MSWD = 1.07, n = 8) for the age a more robust estimate.

of the metamorphic event. This age is undistinguishable within

error with respect to the ages of metamorphism discussed above 5.1.3. Serrania de la Macarena uplift

for samples from the Garzón massif. One sample was analyzed from the metamorphic basement

◦ ◦ ◦ ◦

Sample CB-006 (N2 13 26.5 W75 50 22.0 ) was also taken along of this sierra (Macarena-2, N3 01 45.0 W73 52 13.5 ). It con-

the Zancudo creek a few tens of meters downstream (east) from sists of a melanocratic Bt-Ep-Mc-Pl-Qz mylonitic gneiss with

the location where sample MIVS-41 was collected. In this loca- abundant sphene, suggestive of dynamic metamorphism under

tion, metatexic migmatites of metasedimentary origin display well at least upper-greenschist-grade conditions. Sub-grain rotation

developed stromatic structures, characterized by an interleaving of deformation mechanisms observed in Qz and Fsp crystals suggest

5–10 cm thick granitic leucosomes with laterally persistent bands intermediate temperatures for the mylonitization event of at least

◦

of Bt-Hbl gneisses. The analyzed sample is a sillimanite-bearing 400 C (Passchier and Trouw, 2005), that did not generate a strong

Bt-rich gneiss with amphibole and clinopyroxene interpreted as a metamorphic imprint on U–Pb systematics of the analyzed zircon

melanosome from these metatexites. Zircons recovered are mostly crystals (Fig. 4). CL images from handpicked zircons show that all

rounded to subrounded in shape, displaying width:length ratios of the grains have oscillatory-zoned textures indicative of igneous

1:2 to 1:3 and average sizes between 50 and 250 ␮m; CL imaging crystallization (Fig. 4, supplementary CL ﬁle), and most of the point

66 M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77

Payara-1, La Rastra-1, Solita-1, Mandur-2, Caiman-3, and Mandur-

3 wells (Fig. 2), which drilled through basement rocks at depths

below 1064 m, 940 m, 1120 m, 1710 m, 2350 m and 2290 m, respec-

tively. These are not the only wells that reached the crystalline

basement in the region but, to our knowledge, are most – if not

all – of the few that recovered cores accessible for sampling. These

cores represent the only available means to study the petrology and

geochronology of the basement of the proximal Andean foreland in

Colombia. Samples processed from the Mandur-3 and La Rastra-1

wells did not yield zircon concentrates so they will not be discussed

further. They are an epidote-amphibolite-facies metabasite, and a

kyanite-bearing Grt-Cpx-Hbl-Bt-Pl-Qz melanocratic schist, respec-

tively.

5.2.1. Putumayo basin basement cores

◦ ◦

The Payara-1 well (N2 07 31.3 W74 33 35.9 ) was drilled in

the northern part of the basin and is the northernmost of the

basement wells presented in this study piercing the crystalline

basement along the western ﬂank of the Macarena arch (Fig. 2a).

The core sample consists of an Opx-Sil-Grt-Hbl-Bt-Pl-Qz migmatitic

gneiss interpreted to have been metamorphosed under granulite-

Fig. 4. U–Pb concordia diagram for the sample analyzed from the basement of the

Serrania de la Macarena. grade conditions. CL images of zircons recovered from this sample

have oscillatory-zoned cores that indicate an igneous origin, and

appear mantled by thin rims of unzoned bright metamorphic zircon

analyses performed were >95% concordant. A concordia age cal-

(inset, Fig. 6a). Small zircons grains tend to show a subtle fad-

culated with 19 individual analyses yields a value of 1461 ± 10 Ma

ing of the original igneous growth zoning, a feature which can be

(MSWD = 0.37, n = 19) for the igneous precursor of these mylonites.

due to the effect of partial solid-state metamorphic recrystalliza-

In some grains, the normal igneous textures appear to be partially

tion under granulite-grade conditions (e.g. Connelly, 2001). This

obliterated by incipient recrystallization of the zircons probably

observation is also supported by the U–Pb isotopic data, where it is

due to the mylonitization event, but spot analyses performed in

evident that spot analyses performed in smaller grains are slightly

these areas resulted in only slightly discordant ages that are very

discordant and lie along a chord that trends towards the age of

close to those obtained from the unaffected portions of the grains,

metamorphism as the lower intercept (Fig. 6a). Calculation of a

thus not allowing to place any constraints on the age of the Pb-loss

concordia age using 16 core analyses that are <3% discordant yields

event. Some of the imaged grains also display bright-CL rims that

an age of 1606 ± 6 Ma (MSWD = 0.97, n = 16) for the crystallization

appear to be mantling the igneous crystals, which could very likely

of the igneous protolith. Given the thin width of the metamorphic

be low-U overgrowths of metamorphic origin. However, due to its

overgrowths (<30 ␮m), analyses were performed using an 18 ␮m

␮

small size of <10 m in width, they were not possible to date with

diameter spot size with the ion-counter conﬁguration. Seven analy-

our analytical approach.

ses were acquired from these overgrowths, four of them being <4%

discordant. Of these four, one is 10% normal discordant, another

5.2. The basement underlying the foreland basins one is 8% reverse discordant, and the last one is 5% discordant but

is signiﬁcantly older than the others and lying along a chord that

The North Andean foreland basins of Colombia can broadly be goes towards the age of the igneous cores. This last analysis is an

divided in two sub-basin, the Putumayo to the south which rep- example of a mixed ablation spot, and incorporation of core mate-

resents the northern extension of the Maranon-Oriente˜ basins of rial can be clearly seen in the detailed CL (Plate 4, supplementary

Peru and Ecuador, and the Llanos to the north that continues north- CL ﬁle). The four <4% discordant analyses yield a concordia age

eastward into Venezuela (Figs. 1 and 2). These two basins are of 986 17 Ma (MSWD = 0.49) for the granulite-grade event, con-

separated by a series of NW trending basement structures, namely sidered to be the best estimate for the age of metamorphism of

206 207

the Macarena-Chiribiquete structural high and the Vaupes arch, this gneiss. A Pb/ Pb weighted mean age of the six non-mixed

which extend from the borders with Peru and Brazil in southeast- analyses deﬁnes an equivalent but less-precise age of 985 ± 23 Ma

ern Colombia to the Serrania de la Macarena next to the Andean (MSWD = 0.70), but as in previous samples the concordia age is

chain (Fig. 2). preferred. Note the very low U concentrations measured on the

Many exploratory wells in the foreland basins of Colombia have overgrowths, estimated between 15 and 20 ppm (supplementary

drilled below the unconformity between the crystalline basement data).

◦ ◦

and the overlying Phanerozoic sedimentary cover, but not many The Solita-1 well (N0 52 28.6 W75 37 21.3 ) was drilled

of them have retrieved core samples. The depth to the crystalline in the central part of the basin, coring basement rocks of

basement is highly variable and depends on the relative position of the Florencia arch. The analyzed sample consists of strongly

each well with respect to the foredeep and the horst/graben base- deformed Amp-Bt-Ep-Pl-Qz migmatitic gneisses, whose textures

ment structures, but in general the basement is shallower in the suggest syn-deformational metamorphism and melting under

Putumayo basin than in the Llanos. In the Putumayo basin, on those amphibolite-grade conditions. Recovered zircons are small in size,

␮

wells where basement cores have been recovered, Cretaceous rocks generally <150 m in length, displaying 1:2 to 1:4 width:length

directly overlie the Precambrian units whereas a section of Paleo- ratios. Most of the crystals are cloudy with reddish and brownish

zoic sediments in excess of 1000 m in thickness has been drilled in tones and show strong suppression of their CL emission, observa-

several locations around the Llanos basin. tions that suggest a considerable degree of metamictization (inset,

For the purposes of this study, we sampled six different Fig. 6b). Xenocrystic cores are common in most of the imaged crys-

exploratory wells that recovered core samples from the crystalline tals and U–Pb analyses performed produce a complex concordia

basement of the Putumayo Basin. From north to south they are the plot (Fig. 6b). Most of the spots placed on the dark overgrowths

M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77 67

of crystallization from a silicate melt but also display ﬂow and

shearing structures indicative of injection and crystallization under

differential stress conditions. The melanocratic host rocks for the

dikes are Amp-Bt-Pl-Qz gneisses deformed under at least under

amphibolite-grade conditions, in which thin leucocratic stromata

of tonalitic composition were developed parallel to the foliation

of the gneisses suggesting an incipient degree of partial melting.

We thus interpret the overall stromatic morphology as the result

of layer-parallel injection of the syenogranitic melt, although the

presence of thin trondhjemitic neosomes in the gneisses also

indicates some degree of partial melting of the host rocks.

We analyzed two separate samples from this core; one zircon

concentrate was obtained from a sample of an approximately 70 cm

thick coarse-grained leucocratic dike, and the other from the host

melanocratic amphibole-gneisses. Zircons from the gneiss display

complex internal morphologies under CL (Fig. 6c, supplementary

CL ﬁle), characterized by cores with oscillatory zoning patterns

that are enclosed by low-luminescent, high-U rims inferred to

have crystallized under metamorphic conditions. Textures indica-

tive of solid-state recrystallization were also observed, evidenced

as bright margins with lobate terminations inboard of the meta-

morphic overgrowths that clearly crosscut the primary igneous

zonation of the cores (e.g. Hoskin and Black, 2000). Isotopic analy-

ses performed on the low-luminescent metamorphic overgrowths

are concordant to moderately discordant (Fig. 6c). From a cluster

of four concordant analyses we obtained an age of 1019 ± 8 Ma

(MSWD = 0.56, n = 4) for the amphibolite-facies event, similar to

that found in the Solita-1 well but older than the granulite-facies

imprint dated from the Payara-1 well. Most of the cores with

oscillatory-zoned textures appear to pertain to a single popula-

tion variably affected by Pb-loss effects, and a cluster of concordant

grains from this group displays an earliest Mesoproterozoic age

Fig. 5. Photographs from some of the drilling-core samples analyzed during the

of 1592 ± 8 Ma (MSWD = 1.06) for the protolith. Many core analy-

present study. (a) Migmatitic gneisses from the Payara-1 well, (b) Stromatic

ses are strongly discordant and deﬁne a mixing chord between the

migmatites injected by granitic sills from the Mandur-2 well, (c) Metasedimentary

Qz-Fsp migmatites from the Caiman-3 well, and (d) Leucogranites that crosscut the two previously discussed populations with variable superposed Pb-

metamorphic foliation of the migmatites in the Caiman-3 well. loss (gray ellipses in Fig. 6c), while a few cores with non-oscillatory

zoned textures yield older concordant ages up to 1713 Ma inherited

from a possible volcanosedimentary protolith.

appear to be aligned deﬁning a recent Pb-loss event and a weighted Zircons from the leucocratic sills are mostly elongated and pris-

206 207

mean Pb/ Pb age of 1046 23 Ma (Fig. 6b) considered to rep- matic, displaying width:length ratios between 1:3 and 1:5 and

resent the age of metamorphism and melting, calculated using 12 sometimes up to 500 ␮m in length. Internal CL images showed

analyses that are less than 30% discordant. Ellipses shown in blue that the grains have oscillatory-zoned textures indicative of crys-

in Fig. 6b represent analyses that are either xenocrystic cores or tallization from a melt, but some internal complexities are apparent

ablation spots that represent mixtures between the inherited com- from the presence of bright rims surrounding darker cores which

ponent and the ca. 1.05 Ga overgrowths. Older analyses, with ages sometimes appear to truncate previous zoning patterns (Fig. 6d,

of 1.73 and 1.85 Ga, are interpreted as detrital grains from a sedi- supplementary CL ﬁle). Around 60 U–Pb spots were performed

mentary protolith, and some of the discordant analyses appear to over the different textural areas and complexities of the grains

be aligned along a mixing chord between the metamorphic age and but they produced a fairly simple age pattern (Fig. 6d), with all

an inferred ca. 2.0 Ga component. Two important geological events the analyses overlapping concordia and deﬁning a rather homoge-

that affected the western Putumayo basin could be responsible neous population with an age of 1017 ± 4 Ma (MSWD = 0.66). This

for the observed recent Pb loss: (1) hydrothermal water circula- age, interpreted as reﬂecting the timing of crystallization of the

tion from the Cordillera towards the foreland during Oligo-Miocene granitic melt, is more precise but still within error with respect to

Andean uplift pulses and orogenic development (Parra et al., 2009), the age of metamorphism measured from the zircons overgrowths

and (2) thermal effects and hydrothermal water circulation during of the host gneisses described above. We thus consider that peak

nearby late Miocene maﬁc magmatism (Vasquez et al., 2009). regional metamorphism and injection of granitic melt were rela-

◦ ◦

The Mandur-2 well (N0 55 24.5 W75 52 34.1 ) cored basement tively synchronous in this area of the basin as suggested by textural

rocks beneath the west-central part of the basin, and consists of observations and supported by the geochronological results.

◦ ◦

an intercalation of melanocratic migmatitic gneisses and centi- The Caiman-3 well (N0 45 13.6 W76 09 45.4 ) cored approxi-

metric to decimetric coarse-grained leucocratic veins and sills mately 10 m of basement in the southwestern part of the basin,

of muscovite-bearing syenogranites (Fig. 5b). Given the size of sampling a depth interval between 2350 and 2360 m just below

the granitic layers and the lack of evident melanosomes and/or the unconformity with the overlying Cretaceous strata. This core

reaction margins (selvedges) along the contact with the surround- broadly consists of two different rock types: an upper part of felsic

ing gneiss, we interpret these dikes as granitic melts injected migmatites (Fig. 5c), and a lower part of undeformed leucogranites

into the melanocratic migmatitic gneisses, but bearing no genetic that crosscut the foliation of the metamorphic rocks (Fig. 5d). The

relation (as derivation through partial melting) with its more migmatites display leucosomes that are sub-parallel with respect

maﬁc host rock. The granitoid intrusions display clear textures to a subtle foliation deﬁned by the orientation of biotites, quartz and

68 M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77

Fig. 6. U–Pb concordia diagrams for samples analyzed from drill-core samples of the Putumayo basin basement.

plagioclase, and is classiﬁed as a leucocratic diatexite. We analyzed (Fig. 6e, supplementary CL ﬁle). Individual grains are generally not

different zircon fractions for each rock type. larger than 110 ␮m, and metamorphic rims do not exceed 20 ␮m in

Zircons extracted from the migmatites from a segment of the thickness. We performed 85 spot analyses on the xenocrysts utiliz-

core between 2352.6 and 2353.75 m (corresponding to Fig. 5c) have ing a 30 ␮m laser diameter, and 20 analyses on the overgrowths

␮

rounded to sub-rounded external shapes and length:width ratios using a 10 m laser-beam diameter on ion-counter conﬁgura-

from 1:1 to 2:1. CL images revealed a complex internal morphology tion. From the rim analyses, only 12 clustered around an age of

in these grains, characterized by cores with mostly oscillatory- ∼990 Ma (Fig. 6e) while the remaining gave ages that were much

zoning that are mantled by low luminescent thin metamorphic rims older, reﬂecting partial zircon recrystallization with Pb inheritance

M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77 69

or mixing of old core material in the ablation sites. A concordia

age calculated from the rims data yields a value of 989 ± 14 Ma

(MSWD = 0.7, n = 12), interpreted as the age of the metamorphic

event. From the xenocryst core results, 11 of them resulted in

>30% discordant ages and were discarded, while the remaining 74

revealed to be derived from late Paleproterozoic to early Meso-

proterozoic source areas. From the concordia plot of Fig. 6e it can

readily be observed that many of the analyzed xenocrysts have been

affected by varying degrees of Pb-loss, possibly by partial recrystal-

lization during the metamorphic event. If this is the case, and the

observed discordance is effectively related to metamorphism, then

individual ellipses would be slightly displaced from their “true” age

206 207

towards apparent younger Pb/ Pb ages, lying along a discordia

chord that is subparalel to concordia. This effect, however, although

difﬁcult to quantify, would only reinforce the observation that all

of the detrital grains analyzed have crystallization ages older than

about 1.45 Ga. The diverse range of ages obtained for the xenocrys-

tic cores reﬂects the detrital nature for the protolith of this rock

and provides valuable information about the provenance of this

unit. The age spectrum, which is shown in Fig. 7, is dominated by

peak modes at ca. 1470, 1500, 1570, and in the range from 1650 to

1680 Ma.

The second sample analyzed from the Caiman-3 well, corre-

sponding to the lower segment of leucogranites, is a muscovite-

bearing monzogranite taken from the depth interval between

2355.60 and 2355.80 m. Zircons recovered from this sample

have more elongated and prismatic shapes in comparison to the

rounded edges of the zircons recovered from the host migmatites,

and display width:length rations between 1:2 and 1:4 (Fig. 6f,

supplementary CL ﬁle). Most of them are characterized by bright

overgrowths enclosing darker xenocryst cores, and some of these

overgrowths have oscillatory-zoning patterns indicating crystal-

lization from a silicate melt. Analyses from this sample were carried

out the same way as in zircons from the migmatites, using 10 ␮m

ion-counter conﬁguration for the rims and 30 ␮m faraday conﬁgu-

ration for the cores. Twenty-three spots were analyzed from the

overgrowths but only seven of them were younger than ∼1 Ga,

reﬂecting signiﬁcant mixing of older material in most of the abla-

tion pits. A concordia age calculated from these young analyses

yields a value of 952 21 Ma (MSWD = 0.98, n = 7) for the igneous

crystallization event, conﬁrming the cross-cutting relationships

observed from the drill-core. From the xenocrysts, 61 out of the 84

analyses performed are <5% discordant and they yield ages rang-

ing from ca. 1440 to 1700 Ma with distribution peak maxima at

∼

1460, ∼1490, ∼1530, ∼1615 and ∼1677 Ma. This age distribu-

tion closely resembles that of the migmatites from this same well

(Fig. 7), suggesting that these leucogranites may represent anate-

ctic melts derived from metasediments similar to those in which

they are hosted.

Fig. 7. Probability plots for the detrital age components of Mesoproterozoic

metasedimentary units included within the Putumayo Orogen, indicating their

respective ages of metamorphism measured by zircon U–Pb and calculated pro-

tolith maximum depositional ages. Shaded red areas represent the spectra plotted

from the entire dataset of each sample while black solid lines show data ﬁltered to

<5% discordance. In addition to the metasedimentary samples, the inherited com-

ponent of anatectic leucogranites found in the Caiman-3 is plotted, as well as a

synthetic diagram combining all the individual spot ages analyzed from granitoids

of the Mitu–Taraira–Araracuara areas. In the upper portion of the plot, ranges of

relevant magmatic activity from the Proterozoic of Mexico and Colombia are shown

for reference (data from Mexico: Cameron et al., 2004; Weber et al., 2010). Colored

columns have the same coding as Fig. 1 and represent the age ranges for the different

provinces of the Amazon Craton (Tassinari and Macambira, 1999). (For interpreta-

tion of the references to color in this ﬁgure legend, the reader is referred to the web

Fig. 7. version of this article.)

70 M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77

5.3. Cratonic exposures intervals, following the schematic paleogeographic model pre-

sented in Fig. 9 and the correlation of geological events that took

As part of this study, we also analyzed six samples of granitoid place in the different provinces as summarized in Fig. 8.

rocks from the neighboring shield outcropping east of the Putu-

∼

mayo basin in order to: (a) test for the occurrence of late Meso- to 6.1. Pre-Rodinian framework ( 1.3 to 1.1 Ga):

early Neoproterozoic rocks exposed within this largely unknown

portion of the shield, and (b) to use these as a cratonic refer- The position of Amazonia during this time period, constrained

ence for evaluating the detrital zircon populations and protolith by a few paleomagnetic poles obtained from the SW portion of

ages obtained from drill-core samples analyzed from the Putumayo the Amazon Craton, suggest initial oblique collision and continued

basin basement (Fig. 7). Although relevant as a reference for the strike-slip displacement between Laurentia and Amazonia along

ﬁnal discussion, the obtained ages are not strictly crucial for the the Llano-Sunsás segments between ca. 1.2 and 1.15 Ga (Tohver

development of the Putumayo Orogen so the results will only be et al., 2002; D’Agrella-Filho et al., 2008). Additional evidence

brieﬂy mentioned and included in Table 1, while the concordia plots supporting this model include the presence of exotic, Amazonian-

and analytical data are included in supplementary material. afﬁne crust in the Blue Ridge/Mars hill inlier of the southern

In summary, samples PR-3215 and J-263 from the Araracuara Appalachians (Loewy et al., 2003; Tohver et al., 2004a), as well as

basement high (Fig. 2) are both epidote-bearing syenogranitic the timing of ﬁnal inversion and high-grade metamorphism along

gneisses that yield late Paleoproterozoic ages of 1756 ± 18 Ma the Nova Brasilandia intracontinental rift of central-western Brazil

and 1732 ± 24 Ma, respectively. Granitoids from the Apaporis and (Tohver et al., 2004b). Signiﬁcant deformation in both provinces

Vaupes rivers further east (samples PR-3092, AH-1419, CJR-19 culminated in the occurrence of undeformed intrusions, repre-

and AH-1216) are all coarse-grained monzo- and syenogranites sented by the Sunsás granite suite dated at 1076 ± 18 Ma in the

with biotite and amphibole, and yield ages that cluster between Sunsás-Aguapei belt (Boger et al., 2005) and undeformed rhyolitic

1530 and 1588 Ma. Whereas no inheritance was observed in the dikes dated at 1098 10 Ma from the eastern Llano uplift (Mosher,

Araracuara samples, this is a very common feature in the Meso- 1998; Walker, 1992).

proterozoic granites where xenocryst ages generally range from The relative position of Baltica with respect to Laurentia during

ca. 1600 to 2000 Ma, with few restricted grains as old as ∼2.5 Ga. this time period is also shown in Fig. 9, constrained by both paleo-

No evidences for magmatic or high-grade metamorphic events magnetic and geologic data (Cawood and Pisarevsky, 2006; Cawood

younger-than ∼1.5 Ga were found in the exposed shield. et al., 2010; Pisarevsky et al., 2003 and references therein). Prior to

∼

1.25 Ga, Baltica is though to have been attached to the modern

eastern coast of Greenland (Fig. 9a) before it started a late Meso-

6. Discussion. Proposed evolution of the Putumayo orogen proterozoic clockwise rotation on its way to its ﬁnal position within

within a Rodinian context Rodinia (Cawood and Pisarevsky, 2006; Cawood et al., 2010). During

this rotation, accretionary tectonics were triggered along Baltica’s

The participation of the Amazon Craton in the assembly of leading edge during the early stages of the Sveconorwegian orogeny

the Rodinia supercontinent has for long been inferred, using the (Bingen et al., 2008b; Bogdanova et al., 2008).

Bolivian-Brazilian Sunsás-Aguapei orogenic belt as a tie to other

Stenian–Tonian orogenic segments worldwide (Cordani et al., 6.1.1. Geochronological structure of Amazonia’s continental

2009; Hoffman, 1991; Li et al., 2008). Continuation of this Meso- leading margin

Neoproterozoic belt towards the northwest, extending beneath U–Pb zircon geochronological results presented in this study

the Amazon River graben and the north Andean foreland basins is conﬁrm the late Paleo- to early Mesoproterozoic character of the

commonly inferred by some authors, but this assumption has so far crystalline basement rocks exposed in the eastern Colombian low-

only been based on indirect evidence such as: (1) the widespread lands. In this area of the craton, undeformed alkaline granitoids

∼

occurrence of 1 Ga zircon populations in parautochthonous lower with crystallization ages between 1.53 and 1.58 Ga intrude a base-

Paleozoic sequences of the Peruvian Andes (Cardona et al., 2009; ment that is predominantly older than ca. 1.70 Ga, as suggested

Chew et al., 2007, 2008; Cordani et al., 2010), and (2) the occurrence by the ages of inherited zircon xenocrysts found in the Meso-

of Grenville-age inliers in the Andes of Colombia (Fuck et al., 2008; proterozoic intrusives (see supplementary material) and granitic

Li et al., 2008; Restrepo-Pace et al., 1997). The geochronological gneisses sampled from the Araracuara basement window (sam-

results presented in this paper provide the ﬁrst direct evidence that ples J-263 and PR-3215). These results seem to be broadly in

shows the existence of an autochthonous Ectasian-Tonian orogenic agreement with a northwestward extension of the RNJ province

belt along the northwestern margin of Amazonia, which serves from Brazil towards Colombia (Tassinari et al., 1996; Tassinari and

both as a basis for global intercratonic correlations and as a refer- Macambira, 1999; Cordani and Teixeira, 2007). Additionally, late

ence against which Cordilleran inliers and peri-Amazonian crustal Paleo- to earliest Mesoproterozoic protolith ages obtained from

blocks can be compared or correlated. As will be further expanded drilling cores of migmatitic gneisses underlying the Putumayo

below, the new geological and geochronological data presented foreland (wells Mandur-2 and Payara-1, Fig. 2) suggest that, pre-

here suggest that the Meso-Neoproterozoic evolution of NW Ama- vious to the inception of the Putumayo orogen, the late Paleo- to

zonia’s margin is very different from that of the Sunsás-Aguapei early Mesoproterozoic basement of NW Amazonia extended all the

orogen; consequently, we propose the name Putumayo Orogen for way towards the cratonic margin (modern proximal foreland base-

a distinct segment of a Ectasian-Tonian mobile belt in northern ment). In this area, the new information obtained from drill-core

South America, whose paleogeographic signiﬁcance and global tec- samples also shows that sedimentary basins with cratonic prove-

tonic implications should also be distinct from those of the Sunsás nance were developed during mid Mesoproterozoic times, possibly

belt according to the nature and timing of the major geologic events covering the late Paleoproterozoic marginal basement, as evi-

that locally characterized its evolution (Fig. 8). Given the new tim- denced by metasedimentary migmatites from the Caiman-3 well

ing constraints, we propose a three-stage magmatic/metamorphic that yield a maximum depositional age estimated to 1444 ± 15 Ma

history for the Putumayo Orogen, characterized by the devel- and clearly show detrital zircon age spectra dominated by cra-

opment of a fringing-arc complex followed by terrane accretion tonic, mostly RNJP-like ages (Fig. 7). These observations contrast

and ﬁnal ocean closure during continent–continent collision. with the regional structure of the craton in SW Amazonia, where

The following discussion will be subdivided into three temporal the regionally extensive Rondonia-San Ignacio Mesoproterozoic

M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77 71

NW Amazonia N Andes Foreland Basement Laurentia SE Laurentia NE North Andean Inliers SW Amazonia Mexican Terranes (Autochtonous NW Gondwana) (para-autochtonous terranes) SW Baltica (Llano) (Grenville) 900 Regional cooling and localized Low-P Metamorph S Dalane phase v (Post-collisional e relaxation and collapse) Extensional Undeformed Leucogranites P u c Phase t o u Rondônia tin province Post-tectonic pegmatites n Falkenberg phase Migmatization m S o a Peak granulite Metamorphism granites followed by Peak Metamorphism Payara and Caiman wells y u r 1000 Garzon and Las Minas regional cooling “Zapotecan” event o n w s e Agder phase Rigolet Phase O Margaritas Migmatites (Garzon) (Main continental Fringing-arc terrane r a AMCG magmatism g collision event) G collisions o s Strike-slip continuous deform. i g r (Migmatization Sedimentation (Late shearing offshots and final a Ottawan e (Arc-proximal basins) A accretion of the “Paragua block”) e Mandur and Solita wells) n n ? g n Phase ? u Post-collisional O v ? a r Post-tectonic i p Sunsas Granite Suite o granites l Millions of Years (Ma) Millions of Years 1100 e g l Sunsas group “Olmecan” event Arendal phase

i e

e Back-arc Early terrane collisions Adirondian collisional deformation n sedimentation over O O Magmatism Arc Magmatism Metamorphic the continental event. Zr rims r Arc/Backarc magmatism r Garzon Massif margin (?) Dibulla gneiss o Accretion of o (AMCG suites) g (Protolith ages in orthogneisses. older than g Metamorphic Bimodal magmatism 1.25 Ga terranes e event. Zr rims e Passive-margin and Huiznopala, Oaxaca, Novillo) and Sedimentation n ? Jojoncito gneiss n intra-continental rift Shawinigan Sedimentation sedimentation 1200 phase This work This Work Boger et al. (2005); Keppie et al. (2009); Bingen et al. (2008)a; Barker and Reed Bartholomew and Cardona et al. (2010); Santos et al. (2008); Cameron et al. (2004); Bingen et al. (2008)b; (2010); Hatcher (2010); Ordonez-Carmona et al (2007); Cordani et al. (2009); Keppie et al. (2003); Bogdanova et al. (2008) Mosher et al. (2004); Tollo et al. (2004); Cordani et al. (2005); Teixeira et al. (2010); Solari et al. (2003); Mosher et al. (2008); Gower and Krogh Restrepo-Pace et al. (1997) Tohver et al. (2004) Reese and Mosher (2002); (2004) Rivers (1997);

McLelland (1996)

Fig. 8. Events correlation chart for different provinces of Amazonia, Baltica and Laurentia during the time interval from 1200 to 900 Ma, relevant for paleogeographic

correlations discussed throughout the paper. References used for each region are listed in the ﬁgure.

orogen lies outboard of the RNJ and separates the later from the (CB-006) overlying an orthogneissic unit (MIVS-41). In the case

Sunsás-Aguapei orogen (Fig. 1; Bettencourt et al., 2010; Cordani and of the Zancudo creek metatexites, the large proportion of inher-

Teixeira, 2007). Following from the presently available geochrono- ited zircon cores with textures suggesting a metamorphic origin

logic data, we can conclude that a correlative Mesoproterozoic (Supplementary CL ﬁle, Plate 2) is still puzzling, and the domi-

orogenic belt that is equivalent in magnitude to the Rondonia-San nantly unimodal age distribution obtained from these cores implies

Ignacio province of Brazil seems to be missing in northwestern either (1) sedimentary sourcing from a very restricted basin that

South America. drained metamorphic rocks with an age ca. 1.15 Ga, or (2) that

these grains were formed in situ by a previous metamorphic event

6.2. The Colombian–Oaxaquian fringing-arc system (ca. affecting this sedimentary sequence. Although the presently avail-

1.30–1.10 Ga) able data is not sufﬁcient to conclusively rule out any of these two

hypotheses above, it provides strong evidence to infer that meta-

High-grade metasedimentary units dated from the Las Minas morphism was locally occurring ca. 1.15 Ga and was coeval with

and Garzón cordilleran inliers display characteristics that suggest granitic magmatism (e.g. Guapoton gneiss protolith, Fig. 8). Zircon

their protoliths formed in proximity to an active-arc system, such rims of similar age have also been reported from detrital grains

as: (1) the short time gap that exists between estimated maxi- found in the Jojoncito and Dibulla paragneisses from the Guajira

mum depositional ages and those of metamorphism, indicating and Santa Marta massifs, respectively (Cordani et al., 2005), thus

that young DZ populations must approximate the true depositional suggesting that a metamorphic event of this age may have been

age of the sedimentary protoliths (Fig. 7); this observation indi- a more widespread feature within the arc. We conclude that the

cates the occurrence of nearby contemporaneous igneous activity (metamorphosed) sedimentary basins and associated underlying

(e.g. Cawood et al., 1999; Dickinson and Gehrels, 2009), and (2) granites now represented by sequences of the Garzón and Las Minas

the ubiquitous presence of feldspar in all the analyzed samples massif developed in an active-margin setting (similar to active-

implies that their protoliths were probably arkosic sands, with margin assemblage 1 of Cawood et al., 2007) where magmatism

variable proportions of ferromagnesian material needed in order and metamorphism intermittently took place during the age range

to form the observed metamorphic maﬁc-mineral-bearing assem- from 1.32 to 1.1 Ga and, as it is discussed below, they may have

blages. These observations support previous interpretations that evolved as parautochthonous arc terranes outboard of Amazonia.

suggest volcanosedimentary sequences to be the protoliths for the In many Mesoproterozoic paleogeographic reconstructions,

metasedimentary gneisses and felsic granulites of the Garzón mas- Oaxaquia is commonly positioned along the northwestern mar-

sif (Kroonenberg, 1982). gin of Amazonia in close association with the Colombian Andean

Although the stratigraphic relation between the Guapoton inliers, where they have also been interpreted as parautochthonous

orthogneiss and the Vergel metasediments was not observed, it arcs latter to be trapped between colliding continental blocks dur-

is clear that protolith sedimentation of the later unit postdates the ing the assembly of Rodinia (Bogdanova et al., 2008; Cardona

granitic-protolith crystallization of the orthogneiss (Fig. 7). It is pos- et al., 2010; Keppie et al., 2001; Keppie and Dostal, 2007; Keppie

sible that the ca. 1.14 Ga granites correspond to the local basement and Ortega-Gutierrez, 2010; Keppie and Ramos, 1999; Li et al.,

of the area over which the sedimentary sequences now repre- 2008). The Proterozoic basement blocks of Mexico, known as the

sented by the Vergel metasediments were originally deposited, and Novillo gneiss, Huiznopala gneiss, the Oaxacan complex, and the

such a stratigraphic relationship could also be the case for the Las Guichicovi complex (Fig. 1 in Keppie and Ortega-Gutierrez, 2010),

Minas massif with the Zancudo creek metasedimentary migmatites are characterized by a similar Proterozoic history consisting of

72 M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77

Fig. 9. Proposed tectonic evolution of the Putumayo orogen from the late Mesoproterozoic to early Neoproterozoic and proposed paleogeographic correlations between

Amazonia, Baltica and Laurentia. Other blocks and cratons were omitted for simplicity. Outline and provinces of Laurentia modiﬁed from Cawood et al. (2007); Baltica from

Bingen et al. (2008b) and Bogdanova et al. (2008); Amazonia from Cordani et al. (2000). See text for discussion and other references used.

granitic intrusives with arc and backarc chemical afﬁnities dur- commonly evolving “Colombian–Oaxaquian” peri-Amazonian

ing the interval ∼1.3 to 1.15 Ga, intrusion of AMC complexes fringing arc system located outboard of Amazonia’s leading edge

around 1.01 Ga, and high-grade granulite-facies metamorphism during late Mesoproterozoic times (Figs. 9a and 10).

at around 0.99 Ga (Cameron et al., 2004; Keppie and Ortega- According to Busby et al. (1998), long-lived convergent mar-

Gutierrez, 2010; Solari et al., 2003; Weber and Hecht, 2003; Weber gins facing a large ocean basin may evolve through three distinct

and Kohler, 1999). Similarities in Pb isotopic compositions, U–Pb phases: (1) a strongly extensional intraoceanic-arc phase, (2) a

ages of granulite-grade rocks, and Paleozoic fossil faunas from mildly extensional arc system, and (3) a compressional continental-

Colombia and Mexico led Ruiz et al. (1999) to suggests a cor- arc phase following accretion of the fringing-arc terranes. We

relation between the Proterozoic inliers of these two regions, propose that our hypothesized Colombian–Oaxaquian fringing arc

specially between the Garzón, Santa Marta and Guichicovi inliers, may have evolved in a similar fashion, as many of these stages

correlation that has found further support with recent zircon Hf can potentially be identiﬁed from its Mesoproterozoic geological

isotopic data (Weber et al., 2010). Following the various lines record: initiation of the strongly extensional arc phase would be

of evidence that tie the Proterozoic evolution of the Colombian represented by the occurrence of 1.3 Ga rift related basalts (now

and the Mexican inliers, we include the Colombian cordilleran transformed into maﬁc granulites) of the north Oaxaca complex

inliers and the Mexican terranes in our reconstruction as part of a (Keppie and Dostal, 2007) and bimodal igneous suites with backarc

M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77 73

Fig. 10. Schematic section for the proposed conﬁguration of the Colombian–Oaxaquian fringing-arc system at ca. 1.15 Ga.

Modiﬁed from Busby (2004).

geochemical signatures of the Novillo gneiss (Keppie and Ortega- ﬁnal collapse of the arc against the continental margin at the same

Gutierrez, 2010). Rifting from Amazonia would have been followed time as decreased absolute rates of subduction generate the mag-

by the development of an intraoceanic arc (phase 2) character- matic lull (e.g. Busby, 2004). The termination of magmatic activity

ized by widespread arc-related juvenile magmatism between 1.3 along the peri-cratonic arc marks the initiation of collisional events

and 1.2 Ga such as that found in Oaxaquia (Keppie et al., 2001; recorded in the Putumayo orogen.

Keppie and Ortega-Gutierrez, 2010; Weber and Hecht, 2003; Weber

and Kohler, 1999; Weber et al., 2010), later evolving towards 6.3. Rodinia assembly initiation: terrane and arc accretion onto

more mature isotopic compositions like those exempliﬁed by Amazonia’s cratonic margin (1.1–1.01 Ga)

the Guapotón orthogneiss in the Garzón massif (Restrepo-Pace

et al., 1997). Coeval accumulation of thick volcanosedimentary Although largely obliterated by the later granulite-grade meta-

sequences may have taken place during this phase, resulting morphic overprint, there are geological and geochronological

in units that are now represented by thrust slices of the El evidences supporting the existence of an early metamorphic event

Vergel migmatites included within the Garzón group; in this unit, between 1.05 and 1.01 Ga, both in the Andean cordilleran inliers

metasedimentary felsic granulites and gneisses metamorphosed at and in the basement of the Putumayo basin. Metamorphism of the

ca. 0.99 Ga yield estimated maximum depositional ages that are Las Margaritas unit in the eastern ﬂank of the Garzón massif is con-

generally younger than 1.15 Ga as evidenced by their inherited DZ strained to 1015 ± 7.8 Ma by U–Pb SHRIMP dating of a leucosome

component. The detrital zircon signatures from these units can be from a migmatitic paragneiss, as well as by a Sm–Nd garnet-whole

explained in terms of derivation from granitic sources included rock isochron age of 1034 ± 16 Ma (Cordani et al., 2005). Simi-

within the same Colombian–Oaxaquian arc terrane (Fig. 7), while lar ages are also reported in this article for the basement of the

the lack of detritus sourced from continental Amazonia is evident Putumayo basin, where amphibolite-grade migmatites identiﬁed

by the paucity of ages older than 1.5 Ga (Rio Negro-Juruena) in the in the Mandur-2 and Solita-1 wells yield ages of 1019 ± 8 Ma and

spectrum. 1046 ± 23 Ma, respectively (Fig. 9), supporting an early metamor-

Conversely, geochronological results from core samples recov- phic event that we hypothesise could be the result of accretionary

ered in the Putumayo basin basement do not support the events against this segment of the continental margin. This event,

existence of a late Mesoproterozoic active margin developed on an age-equivalent for the Laurentian Ottawan orogeny (McLelland

autochthonous Amazonia crust. Instead, our data show that the cra- et al., 1996), has been noted by Santos et al. (2008) to be absent

tonic margin of northwestern South America is characterized by from the geological record in the Sunsás orogen of southwestern

Stenian–Tonian metamorphic reworking of late Paleoproterozoic Amazonia.

basement and associated mid-Mesoproterozoic cover sequences, In Oaxaquia, late Mesoproterozoic tectonothermal events have

but was otherwise relatively stable with only sedimentation occur- also been identiﬁed in the age range between 1.1 and 1.07 Ga (Solari

ring (i.e. Caiman-3 cores sedimentary protoliths) and no magmatic et al., 2003; Weber et al., 2010), where they have been grouped

events were identiﬁed in the interval from ca. 1.59 to 1.01 Ga. Con- within the Olmecan orogeny (Fig. 8). Following the connections

sequently, in our schematic reconstruction of Fig. 10, we include all previously drawn between Oaxaquia and the Colombian inliers,

the late Mesoproterozoic Colombian and Mexican inliers in a com- we interpret these metamorphic ages as constraining the timing of

mon fringing arc system outboard of Amazonia instead of separated accretion of the Colombian–Oaxaquian parauthochtonous arc onto

in two sub-parallel arcs as proposed by Weber et al. (2010). Amazonia’s continental margin. This event was probably shortly

Following this period of intensive arc plutonism in the Colom- followed by slab-break off and melting of the lower crust, leading to

bian and Mexican inliers there was an interval of magmatic the generation of the AMC intrusive complexes that are widespread

quiescence that spanned the age range between 1100 and 1050 among the Oaxaquian terranes (Weber et al., 2010) and possibly

(Fig. 9). A possible reason for the sudden shutting down of magma- also present in the Sierra Nevada de Santa Marta massif in the

tism could be a drastic change in the overall stress conditions along northernmost Colombian Andes (Tschanz et al., 1974).

the arc, such as those that could derive from transitioning between It is worth noting that, in Baltica, metamorphism of the Bamble

a mildly extensive regime to compressive one (similar to the tran- and Kongsberg tectonic wedges marks the timing of early terrane

sition from phase 2 to phase 3 in Busby et al., 1998). A switch of this accretions onto Fennoscandian crust and the collision of Telemarkia

type could have been responsible for increased plate coupling along against the Idefjorden terrane (the Arendal phase, Bingen et al.,

the margin, resulting in continent-directed trench migration and 2008b). The Bamble and the Kongsberg terranes comprise variably

74 M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77

metamorphosed supra-subduction complexes whose metamor- identiﬁed in southern Scandinavia as continued deformation along

phic ages constrain these collisions to have occurred between the mylonite zone between 980 and 970 Ma, foreland basin propa-

∼

1140 and 1090 Ma, clearly earlier that the timing of initial gation, and eclogite-facies metamorphism on the eastern segment

accretion along Amazonia’s margin as recorded in the Putu- at 970 Ma (Bingen et al., 2008b; Johansson et al., 2001). These late

mayo Orogen and Oaxaquia. Additionally, marked differences tectonothermal events are also recorded in the Colombian inliers

between the detrital zircon age spectra of Telemarkia’s metased- where metatexic migmatites of the Las Minas massif yield ages

imentary units (Bingen et al., 2001, 2003), and those from NW of 972 ± 12 Ma for the anatectic event (sample CB-006), similar to

autochtonous/parautochtonous Amazonia (this study) lead us to other ages of ca. 0.97 Ga found elsewhere in Oaxaquia (Cameron

conclude that, regardless of the exotic or indigenous origin of Tele- et al., 2004; Weber et al., 2010). In the Putumayo basin, the unde-

markia with respect to Fennoscandia, an Amazonian ancestry for formed leucogranite that intrudes the migmatites cored in the

this terrane and/or its accretion to Baltica at ca. 1.1 Ga by early Caiman-3 well provides a minimum age of 952 ± 19 Ma for perva-

collisional interactions with Amazonia are both very unlikely. sive deformation occurring in this sector of the Putumayo orogen.

This age is similar to that obtained for undeformed granitic peg-

6.4. Final Rodinia assembly: collision along the matites in Oaxaquia, constrained to ca. 0.97 Ga as discussed by

Putumayo-Sveconorwegian orogen (1.00–0.98 Ga) Solari et al. (2003).

In different parts of the Colombian Andes, medium- to low-

New zircon U–Pb data presented in this paper demonstrate the temperature cooling of the high-grade basement of the cordilleran

existence of a Tonian orogenic belt in NW South America that inliers is constrained by K–Ar and Ar–Ar ages that mostly clus-

is buried under the Andean foreland basin sequences, providing ter in a restricted range from 970 to 910 Ma (Cordani et al., 2005;

a direct link to correlate granulite-facies tectonothermal events Restrepo-Pace et al., 1997). These ages imply relatively fast rates

occurring in NW cratonic Amazonia, the Colombian Cordilleran of exhumation and cooling for the granulites of the Colombian

inliers, Oaxaquia, and arguably also the Sveconorwegian orogen cordilleran inliers following the 990 Ma metamorphic peak.

(Fig. 9). Finally, metamorphic rims in zircons from the Santander

As noted by Bogdanova et al. (2008), paleogeographic recon- and Jojoncito paragneisses yield U–Pb ages of metamorphism at

structions between Laurentia and Baltica imply the necessity of 864 ± 66 Ma and 916 ± 19 Ma, respectively (Cordani et al., 2005),

a “third continent” in order to explain the timing and geometry distinctly younger than any of the other Proterozoic metamor-

of the Sveconorwegian province, and they suggest collision with phic events reported here. Although inherited zircon analyses from

Amazonia as a feasible tectonic scenario. Available geochrono- the detrital protolith of these gneisses resemble those from other

logical data from granulite-facies rocks in the Sveconorwegian metasedimentary units presented in this paper, the presence of

indicate that crustal shortening was still underway along this ca. 990 Ma zircons in their detrital component indicate that sed-

orogen while extensional regimes were already dominating the imentation of the Bucaramanga and Jojoncito gneisses protoliths

Laurentian Grenville margin (Bingen et al., 2008b; Bogdanova et al., postdated the regional granulite-grade metamorphic event and

2008; Gower and Krogh, 2002; Gower et al., 2008), but as was noted were possibly inﬂuenced by reworking of older Putumayo metaig-

by Bogdanova et al. (2008) they coincide with the Zapotecan event neous and metasedimentary units such as those presented here

in Oaxaquia at ca. 990 Ma (Cameron et al., 2004; Keppie and Ortega- from the Garzón and Minas massifs. In that case, their deposi-

Gutierrez, 2010; Lawlor et al., 1999; Ruiz et al., 1999; Solari et al., tion possibly took place in basins that were internal to the orogen,

2003; Weber and Kohler, 1999). The new geochronological data equivalent to assemblage 3 basins of Cawood et al. (2007).

presented by us demonstrates that this granulite-grade metamor-

phic event at 0.99 Ga is also widespread in the Colombian inliers 7. Concluding remarks

and, most importantly, the basement of the Putumayo Andean

foreland basin; this evidence allows us to extend the correlation (1) Zircon U–Pb geochronological data presented in this con-

previously drawn between Baltica and Oaxaquia to a larger scale, tribution comprise the ﬁrst evidence for the existence of

now to include the north Andean Colombian Cordilleran inliers, the a Meso-Neoproterozoic orogenic belt in autochthonous NW

Putumayo basin basement and thus, cratonic Amazonia. Amazonia, buried underneath Meso-Cenozoic sedimentary

In line with this chronological evidence, our reconstruction sequences of the north Andean Putumayo foreland basin. Sam-

displays ﬁnal collision occurring between Baltica and Amazonia ples distributed among the Garzón and Minas massifs and

along a juxtaposed Putumayo-Sveconorwegian internal orogen at the Putumayo foreland basin basement enclose an area of

ca. 990 Ma, deﬁning a separate belt with a structural trend that lies at least ∼50,000 km that are underlain by crust reworked

almost orthogonal with respect to the Sunsás-Grenville orogenic during Stenian–Tonian times, expanding the known extent of

tract (Fig. 9). Continuation of the Putumayo Orogen in Amazo- metamorphic events in northern South America caused by con-

nia towards the northeast underlying the foreland Llanos basins tinental collisions during Rodinia assembly.

of northern Colombia and Venezuela still awaits for conclusive (2) Although many details about the geochemistry, petrology

evidence, although there are observations that may suggest this and medium- to low-temperature history of the proposed

could be the case; occurrences of Meso- to early Neoproterozoic Putumayo Orogen are still to be discovered, the new geochrono-

tectonothermal events in Venezuela are known from: (1) K–Ar cool- logical data obtained allowed us to identify distinct phases

ing ages in the range from 1.36 to 0.86 Ga from various basement of magmatism and metamorphism that comprise its evolu-

drilling-cores in the Llanos basin presented by Feo-Codecido et al. tion. We propose that igneous and sedimentary protoliths

(1984), (2) U–Pb LA-ICP-MS ages from basement drilling cores in for the metamorphic units exposed in the cordilleran ter-

the La Vela gulf dated between ca. 1.1 and 1.3 Ga (Baquero et al., ranes formed during mid- to late Mesoproterozoic times in

2011; Marvin Baquero, personal communication), and (3) the wide a parauthochtonous fringing-arc system to Amazonia, herein

variety of high-grade metamorphic rocks closely resembling the termed the Colombian–Oaxaquian arc, later to be accreted

granulites of the Colombian Andes such as those found in the Nirgua to the continental margin at ca. 1.02 Ga and trapped within

inlier of the northern Merida Andes and other locations discussed Rodinian internal collisional orogens at 0.99 Ga.

by Grande and Urbani (2009) (and references therein). (3) In addition to the differences in timing for the metamorphic

Following collision, shortening and crustal thickening may events with respect to the Sunsás-Aguapei orogen, protolith

have continued along the Putumayo-Sveconorwegian orogen, ages for samples recovered from the basement of the Putumayo

M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77 75

basin suggest that there are marked differences with respect to References

the Mesoproterozoic evolution of the SW Amazonian margin,

Aleman, A., Ramos, V., 2000. Northern Andes. In: Cordani, U.G., Milani, E.J.,

and we suggest that a orogenic belt correlative to the Rondonia

Thomaz-Filho, A., Campos, D.A. (Eds.), Tectonic Evolution of South America. 31st

– San Ignacio province may be lacking in northwestern South

International Geological Congress, Rio de Janeiro, pp. 453–480.

America. Alvarez, J., Cordani, U.G., 1980. Precambrian basement within the septentrional

Andes: age and geological evolution. In: 26ieme Congr. Geol. Int., Paris, p. 10.

(4) The consistency of the metamorphic ages obtained from the

Baquero, M., Grande, S., Urbani, F., Cordani, U., Sato, K., Schaaf, P., Hall, C., Mendi,

granulite-grade rocks in the cordilleran inliers and the foreland 40 39

D., Azancot, M., 2011. New LA-ICP-MS U–Pb zircon dating, Ar- Ar and Sm-Nd

basement, all of them clustering around ca. 990 Ma, reinforce model ages: Evidence of the Grenvillian event in the basement of the Falcón and

Maracaibo basins, northwestern Venezuela. In: 14th Latin American Geological

correlations between the Colombian and the Mexican inliers

Congress, Symposium Tectonic evolution of Western Gondwana: Linking Pre-

and add new links between these terranes and cratonic Amazo-

cambrian basement architecture with terrane processes, Medellín, Colombia,

nia. The metamorphic history proposed here for the Putumayo Abstract, v.1, pp. 320–321.

Orogen is more consistent with collisional interactions against Barker, D.S., Reed, R.M., 2010. Proterozoic granites of the Llano Uplift Texas: a

collision-related suite containing rapakivi and topaz granites. Geological Society

the Sveconorwegian orogen of Baltica at the heart of Rodinia,

of America Bulletin 122 (1–2), 253–264.

as opposed to against the Laurentian Grenville province as

Bartholomew, M.J., Hatcher, R.D., 2010. The Grenville orogenic cycle of southern

has been commonly considered. It should be noted, however, Laurentia: unraveling sutures, rifts, and shear zones as potential piercing points

for Amazonia. Journal of South American Earth Sciences 29 (1), 4–20.

that the new data presented in this study do not necessar-

Bayona, G., Jiménez, G., Silva, C., Cardona, A., Montes, C., Roncancio, J., Cordani, U.,

ily preclude correlations that suggest a long-lived connection

2010. Paleomagnetic data and K–Ar ages from Mesozoic units of the Santa Marta

between Amazonia and Baltica throughout the Mesoprotero- Massif: a preliminary interpretation for block rotation and translations. Journal

of South American Earth Sciences 29 (4), 817–831.

zoic and part of the Paleoproterozoic (the SAMBA connection,

Bayona, G., Rapalini, V., Constazo-Alvarez, V., 2006. Paleomagnetism in Mesozoic

Johansson, 2009), but we chose a paleogeographic model which

rocks of the northern Andes and its implications in Mesozoic tectonics of north-

is in line with other paleomagnetic (D’Agrella-Filho et al., 2008; western South America. Earth, Planets and Space 58, 1255–1272.

Bettencourt, J.S., Barbosa Leite, W., Salina Ruiz, A., Matos, R., Leonelo Payolla, B.,

Tohver et al., 2002), thermochronologic (Tohver et al., 2006)

Tosdal, R.M., 2010. The Rondonian-San Ignacio Province in the SW Amazo-

and isotopic (Loewy et al., 2003; Tohver et al., 2004a) data that

nian Craton: an overview. Journal of South American Earth Sciences 29 (1),

strongly support collisional interactions between Laurentia and 28–46.

Bingen, B., Andersson, J., Soderlund, U., Moller, C., 2008a. The Mesoproterozoic in

Amazonia along the Sunsás margin during mid- to late Meso-

the Nordic countries. Episodes 31 (1), 29–34.

proterozoic times.

Bingen, B., Birkeland, A., Nordgulen, O., Sigmond, E., 2001. Correlation of supracrustal

(5) The existence of the Stenian–Tonian Putumayo Orogen in sequences and origin of terranes in the Sveconorwegian orogen of SW Scandi-

NW South America also has implications for peri-Gondwanan navia: SIMS data on zircon in clastic metasediments. Precambrian Research 108

(3–4), 293–318.

terrane tectonics after the breakup of Rodinia such as: (1) it pro-

Bingen, B., Nordgulen, O., Sigmond, E.M.O., Tucker, R., Mansfeld, J., Hogdahl, K.,

vides a cratonic reference for evaluating the afﬁnity of crustal

2003. Relations between 1.19-1.13 Ga continental magmatism, sedimentation

blocks with inferred Amazonian ancestries. For example, it and metamorphism Sveconorwegian province, S Norway. Precambrian Research

124 (2–4), 215–241.

strengthens reconstructions that correlate the Proterozoic

Bingen, B., Nordgulen, O., Viola, G., 2008b. A four-phase model for the Sveconorwe-

inliers of Mexico, Colombia and autochthonous Amazonia crust

gian orogeny, SW Scandinavia. Norwegian Journal of Geology 88 (1), 43–72.

(discussed above), and (2) it provides a feasible source area Bogdanova, S.V., Bingen, B., Gorbatschev, R., Kheraskova, T.N., Kozlov, V.I., Puchkov,

V.N., Volozh, Y.A., 2008. The East European Craton (Baltica) before and during

for the origin of “Grenville-age” detritus found in terranes that

the assembly of Rodinia. Precambrian Research 160 (1–2), 23–45.

may have interacted with northern Amazonia at some point

Boger, S., Raetz, A., Giles, D., Etchart, E., Fanning, C., 2005. U–Pb age data from the

in their history (e.g. Maranon˜ complex, Cardona et al., 2009; Sunsás region of Eastern Bolivia, evidence for the allochthonous origin of the

Paragua Block. Precambrian Research 139 (3–4), 121–146.

Maya block, Weber et al., 2008; Avalonian terranes, Strachan

Busby, C., 2004. Continental growth at convergent margins facing large ocean basins:

et al., 2007; Ganderian-type massifs, Gutierrez-Alonso et al.,

a case study from Mesozoic convergent-margin basins of Baja California Mexico.

2005, Nance et al., 2007; Finnmarkian Nappes, Corfu et al., 2007, Tectonophysics 392 (1–4), 241–277.

Busby, C., Smith, D., Morris, W., Fackler-Adams, B., 1998. Evolutionary model for

among others).

convergent margins facing large ocean basins: Mesozoic Baja California, Mexico.

Acknowledgements Geology 26 (3), 227–230.

Cameron, K.L., et al., 2004. U–Pb geochronology and Pb isotope compositions of

leached feldspars: constraints on the origin and evolution of Grenvillian rocks

This research beneﬁted from funding provided to M.I. by from eastern and southern Mexico. In: Tollo, R.P., Corriveau, L., McLelland, J.B.,

Bartholemew, G. (Eds.), Proterozoic Tectonic Evolution of the Grenville Orogen

Ecopetrol-ICP, the GSA student Grant #9184-09 and a Chevron-

in North America. Geological Society of America Memoir, pp. 755–769.

Texaco summer Grant through the University of Arizona. The

Cardona, A., Chew, D., Valencia, V.A., Bayona, G., Miskoviˇ c,´ A., Ibanez-Mejía,˜ M.,

Laserchron center is partially funded by NSF-EAR Grants #0443387 2010. Grenvillian remnants in the Northern Andes: Rodinian and Phanerozoic

and #0732436. The authors would like to thank the Colombian paleogeographic perspectives. Journal of South American Earth Sciences 29 (1),

92–104.

Instituto Nacional del Petroleo (ICP-ECOPETROL) and the Litoteca

Cardona, A., Cordani, U.G., Ruiz, J., Valencia, V.A., Armstrong, R., Chew, D., Nutman,

Nacional de Colombia for allowing access to the core samples.

A., Sanchez, A.W., 2009. U–Pb zircon geochronology and Nd isotopic signatures

M.I. would specially like to thank Monica Carvalho for help with of the pre-Mesozoic metamorphic basement of the eastern Peruvian Andes:

growth and provenance of a late Neoproterozoic to carboniferous accretionary

ﬁgure elaboration, Camilo Bustamante for assistance during ﬁeld-

orogen on the northwest margin of Gondwana. Journal of Geology 117 (3),

work, Kendra Murray for editorial improvements and Ana Milena 285–305.

Rangel for assistance during core sampling at the Litoteca Nacional. Cardona-Molina, A., Cordani, U.G., MacDonald, W.D., 2006. Tectonic correla-

tions of pre-Mesozoic crust from the northern termination of the Colombian

Insightful comments from reviewers Alan Collins and David Chew

Andes, Caribbean region. Journal of South American Earth Sciences 21 (4),

as well as the editorial assistance of Peter Cawood are greatly appre- 337–354.

ciated as they helped improve the ﬁnal version of this manuscript. Cawood, P.A., Nemchin, A.A., Leverenz, A., Saeed, A., Balance, P.F., 1999. U/Pb dating

of detrital zircons: implications for the provenance record of Gondwana margin

This paper is specially dedicated to the memory of Prof. Dr. Thomas

terranes. Geological Society of America Bulletin 111 (8), 1107–1119.

Van der Hammen for his pioneering contributions on the geology

Cawood, P.A., Nemchin, A.A., Strachan, R., Prave, T., Krabbendam, M., 2007. Sedi-

of Colombia and the Amazonas region. mentary basin and detrital zircon record along East Laurentia and Baltica during

assembly and breakup of Rodinia. Journal of the Geological Society of London

164, 257–275.

Appendix A. Supplementary data Cawood, P.A., Pisarevsky, S.A., 2006. Was Baltica right-way-up or upside-down in

the Neoproterozoic? Journal of the Geological Society of London 163, 753–759.

Cawood, P.A., Strachan, R., Cutts, K., Kinny, P.D., Hand, M., Pisarevsky, S., 2010.

Supplementary data associated with this article can be found, in

Neoproterozoic orogeny along the margin of Rodinia: Valhalla orogen, North

the online version, at doi:10.1016/j.precamres.2011.09.005. Atlantic. Geology 38 (2), 99–102.

76 M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77

Chew, D., Kirkland, C., Schaltegger, U., Goodhue, R., 2007. Neoproterozoic glaciation Jimenez Mejia, D.M., Juliani, C., Cordani, U.G., 2006. P-T-t conditions of high-grade

in the Proto-Andes: tectonic implications and global correlation. Geology 35 metamorphic rocks of the Garzón Massif, Andean basement, SE Colombia. Jour-

(12), 1095–1098. nal of South American Earth Science 21 (4), 322–336.

Chew, D.M., Magna, T., Kirkland, C.L., Miskovic, A., Cardona, A., Spikings, R., Johansson, A., 2009. Baltica Amazonia and the SAMBA connection – 1000 million

Schaltegger, U., 2008. Detrital zircon ﬁngerprint of the Proto-Andes: evi- years of neighbourhood during the Proterozoic? Precambrian Research 175

dence for a Neoproterozoic active margin? Precambrian Research 167 (1–2), (1–4), 221–234.

186–200. Johansson, L., Moller, C., Soderlund, U., 2001. Geochronology of eclogite facies

Collins, A.S., Santosh, M., Braun, I., Clark, C., 2007. Age and sedimentary provenance metamorphism in the Sveconorwegian province of SW Sweden. Precambrian

of the Southern Granulites South India: U–Th–Pb SHRIMP secondary ion mass Research 106 (3–4), 261–275.

spectrometry. Precambrian Research 155 (1–2), 125–138. Johnston, S., Gehrels, G., Valencia, V., Ruiz, J., 2009. Small-volume U–Pb zircon

Connelly, J., 2001. Degree of preservation of igneous zonation in zircon as a signpost geochronology by laser ablation-multicollector-ICP-MS. Chemical Geology 259

for concordancy in U/Pb geochronology. Chemical Geology 172 (1–2), 25–39. (3–4), 218–229.

Cordani, U.G., Sato, K., Teixeira, W., Tassinari, C.C.G., Basei, M.A.S., 2000. Crustal evo- Kemp, A.I.S., Gray, C.M., 1999. Geological context of crustal anatexis and granitic

lution of the South American platform. In: Cordani, U.G., Milani, E.J., Thomaz magmatism in the northeastern Glenelg River complex, western Victoria. Aus-

Filho, A., Campos, D.A. (Eds.), Tectonic Evolution of South America. 31st Inter- tralian Journal of Earth Sciences 46 (3), 407–420.

national Geological Congress. Rio de Janeiro, pp. 19–40. Keppie, J., Dostal, J., Ortega-Gutierrez, F., Lopez, R., 2001. A Grenvillian arc on the

Cordani, U.G., Cardona, A., Jimenez Mejia, D.M., Liu, D., Nutman, A., 2005. margin of Amazonia: evidence from the southern Oaxacan complex, southern

Geochronology of Proterozoic basement inliers in the Colombian Andes: tec- Mexico. Precambrian Research 112 (3–4), 165–181.

tonic history of remnants of a fragmented Grenville belt. Geological Society of Keppie, J.D., Dostal, J., 2007. Rift-related basalts in the 1.2–1.3 Ga granulites of the

London, Special Publications 246, 329–346. northern Oaxacan complex, southern Mexico: evidence for a rifted arc on the

Cordani, U.G., Fraga, L.M., Reis, N., Tassinari, C.C.G., Brito-Neves, B.B., 2010. On the northwestern margin of Amazonia. Proceedings of the Geologists Association

origin and tectonic signiﬁcance of the intra-plate events of Grenvillian-type age 118, 63–74.

in South America: a discussion. Journal of South American Earth Sciences 29 (1), Keppie, J.D., Ortega-Gutierrez, F., 2010. 1.3–0.9 Ga Oaxaquia (Mexico): remnant of

143–159. an arc/backarc on the northern margin of Amazonia. Journal of South American

Cordani, U.G., Teixeira, W., 2007. Proterozoic accretionary belts in the Amazonian Earth Science 29 (1), 21–27.

Craton. The Geological Society of America, Special Publications 200, 297–320. Keppie, J.D., Ramos, V.A., 1999. Odyssey of terranes in the Iapetus and Rheic oceans

Cordani, U.G., Teixeira, W., D’agrella-Filho, M.S., Trindade, R.I., 2009. The position during the Paleozoic. In: Keppie, J.D., Ramos, V.A. (Eds.), Laurentia-Gondwana

of the Amazonian Craton in supercontinents. Gondwana Research 15 (3–4), Connections Before Pangea. Geological Society of America Special Paper, Boul-

396–407. der, CO.

Corfu, F., Hanchar, J.M., Hoskin, P.W.O., Kinny, P., 2003. Atlas of zircon textures. In: Kovach, A., Fairbairn, H., Hurley, P., Basei, M., Cordani, U., 1976. Reconnaissance

Hanchar, J.M., Hoskin, P.W.O. (Eds.), Zircon. Reviews in Mineralogy and Geo- geochronology of basement rocks from Amazonas and Maranhão basins in

chemistry. Mineralogical Society of America & Geochemical Society. Brazil. Precambrian Research 3 (5), 471–480.

Corfu, F., Roberts, R.J., Torsvik, T.H., Ashwal, L.D., Ramsay, D.M., 2007. Peri- Kroonenberg, S., 1982. A Grenvillian granulite belt in the Colombian Andes and its

Gondwanan elements in the Caledonian Nappes of Finnmark Northern Norway: relation to the Guiana shield. Geologie Mijnbouw 61 (4), 325–333.

implications for the paleogeographic framework of the Scandinavian Cale- Lawlor, P.J., Ortega-Gutiérrez, F., Cameron, K.L., Ochoa-Camarillo, H., Lopez, R., Samp-

donides. American Journal of Science 307 (2), 434–458. son, D.E., 1999. U–Pb geochronology, geochemistry, and provenance of the

D’Agrella-Filho, M.S., Tohver, E., Santos, J.O.S., Elming, S.A., Trindade, R.I.F., Pacca, Grenvillian Huiznopala Gneiss of Eastern Mexico. Precambrian Research 94

I.I.G., Geraldes, M.C., 2008. Direct dating of paleomagnetic results from Precam- (1–2), 73–99.

brian sediments in the Amazon Craton: evidence for Grenvillian emplacement Li, Z.X., Bogdanova, S.V., Collins, A.S., Davidson, A., De Waele, B., Ernst, R.E., Fitzsi-

of exotic crust in SE Appalachians of North America. Earth and Planetary Science mons, I.C.W., Fuck, R.A., Gladkochub, D.P., Jacobs, J., Karlstrom, K.E., Lu, S.,

Letters 267 (1–2), 188–199. Natapov, L.M., Pease, V., Pisarevsky, S.A., Thrane, K., Vernikovsky, V., 2008.

Dickinson, W.R, Gehrels, G.E., 2009. Use of U–Pb ages of detrital zircons to infer Assembly, conﬁguration, and break-up history of Rodinia: a synthesis. Precam-

maximum depositional ages of strata: a test against a Colorado Plateau Mesozoic brian Research 160 (1–2), 179–210.

database. Earth and Planetary Science Letter 288 (1–2), 115–125. Litherland, M., Annels, R.N., Hawkins, M.P., Klinck, B.A., O’Connor, E.A., Pitﬁeld, P.E.J.,

de Souza Gorayeb, P.S., Veloso Moura, C.A., de Oliveira Barbosa, R.C., Matsuda, N.S., Power, G., Darbyshire, D.P.F., Fletcher, C.N.J., Mitchell, W.I., Webb, B.C., 1989.

2005. Caracterizac¸ ão do embasamento da Bacia do Solimões com base em dados The Proterozoic of eastern Bolivia and its relationship to the Andean mobile

petrograﬁcos e geocronologicos em testemunhos de sondagem. Contribuc¸ ões a belt. Precambrian Research 43 (3), 157–174.

geologia da Amazônia 4, 7–15. Litherland, M., Bloomﬁeld, K., 1981. The Proterozoic history of eastern Bolivia. Pre-

Feo-Codecido, G., Smith, F., Aboud, N., Di Giacomo, E., 1984. Basement Paleozoic cambrian Research 15 (2), 157.

rocks of the Venezuelan Llanos Basin. Geological Society of America 162. Loewy, S., Connelly, J., Dalziel, I., Gower, C., 2003. Eastern Laurentia in Rodinia: con-

Forero-Suarez, A., 1990. The basement of the Eastern Cordillera, Colombia – an straints from whole-rock Pb and U/Pb geochronology. Tectonophysics 375 (1–4),

allochthonous terrane in northwestern South America. Journal of South Ameri- 169–197.

can Earth Sciences 3 (2–3), 141–151. Ludwig, K., 1998. On the treatment of concordant uranium-lead ages. Geochimica

Fuck, R.A., Brito Neves, B.B., Schobbenhaus, C., 2008. Rodinia descendants in South et Cosmochimica Acta 62 (4), 665–676.

America. Precambrian Research 160 (1–2), 108–126. Ludwig, K., 2003. User’s Manual for Isoplot 3.00. A Geochronological Toolkit for

Galvis, J., Huguett, A., Ruge, P., 1979. Geologıa de la Amazonia Colombiana. Boletin Microsoft Excel, vol. 4. Berkeley Geochronology Center Special Publication.

Geologico del Ingeominas 22 (3), 3–86. MacDonald, W.D., Hurley, P.M., 1969. Precambrian gneisses from north-

Gaudette, H., Mendoza, V., Hurley, P., Fairbairn, H., 1978. Geology and age of Par- ern Colombia South America. Geological Society of America Bulletin 80,

guaza rapakivi granite, Venezuela. Geological Society of America Bulletin 89 (9), 1867–1872.

1335–1340. Matos, R., Teixeira, W., Geraldes, M.C., Bettencourt, J.S., 2009. Geochemistry and

Gehrels, G.E., Valencia, V.A., Ruiz, J., 2008. Enhanced precision, accuracy, efﬁciency, Nd–Sr isotopic signatures of the Pensamiento Granitoid complex Rondonian-San

and spatial resolution of U–Pb ages by laser ablation-multicollector-inductively Ignacio province, eastern Precambrian shield of Bolivia: petrogenetic constraints

coupled plasma-mass spectrometry. Geochemistry Geophysics Geosystems 9, for a Mesoproterozoic arc setting. Revista do Instituto de Geociencias da USP 9

Q03017. (2), 89–117.

Gómez, J., et al., 2007. Mapa Geológico de Colombia Escala 1:2,800.000. Ingeominas, McLelland, J., Daly, S., McLelland, J.M., 1996. The Grenville orogenic cycle

Bogota. (ca.1350–1000 Ma): an Adirondak perpective. Tectonophysics 265 (1–2),

Gower, C., Krogh, T., 2002. A U–Pb geochronological review of the Proterozoic his- 1–28.

tory of the eastern Grenville province. Canadian Journal of Earth Science 39 (5), Mojica, J., Villaroel, C., Macia, C., 1987. Nuevos aﬂoramientos fosil ˇııferos del Ordov

795–829. ˇııcico Medio (Fm El Higado) al oeste de Tarqui, valle superiordelMagdalena

Gower, C.F., Kamo, S., Krogh, T.E., 2008. Indentor tectonism in the eastern Grenville (Huila,Colombia). Geologıa Colombiana 16, 95–97.

province. Precambrian Research 167 (1–2), 201–212. Mosher, S., 1998. Tectonic evolution of the southern Laurentian Grenville orogenic

Grande, S., Urbani, F., 2009. Presence of high-grade rocks in NW Venezuela of pos- belt. Geological Society of America Bulletin 110 (11), 1357–1375.

sible Grenvillian afﬁnity. In: James, K.H., Lorente, M.A., Pindell, J.L. (Eds.), The Mosher, S., Hoh, A.M., Zumbro, J.A., Reese, J.F., 2004. Tectonic evolution of the Eastern

Origin and Evolution of the Caribbean Plate. Geological Society of London Special Llano Uplift, central Texas: a record of Grenville orogenesis along the southern

Publications, pp. 533–548. Laurentian margin. In: Tollo, R.P. (Ed.), Proterozoic Tectonic Evolution of the

Gutierrez-Alonso, G., Fernandez-Suarez, J., Collins, A., Abad, I., Nieto, F., 2005. Ama- Grenville Orogen in North America. Geological Society of America Memoir 197,

zonian mesoproterozoic basement in the core of the ibero-Armorican Arc: pp. 783–798.

Ar-40/Ar-39 detrital mica ages complement the zircon’s tale. Geology 33 (8), Mosher, S., Levine, J.S.F., Carlson, W.D., 2008. Mesoproterozoic plate tectonics: a

637–640. collisional model for the Grenville-aged orogenic belt in the Llano uplift, central

Harrington, H.J., Kay, M., 1951. Cambrian and Ordovician faunas of eastern Colombia. Texas. Geology 36 (1), 55–58.

Journal of Paleontology 25 (5), 655–668. Nance, R.D., Murphy, J.B., Strachan, R.A., Keppie, J.D., Gutiérrez-Alonso, G.,

Hoffman, P., 1991. Did the breakout of Laurentia turn Gondwanaland inside-out. Fernández-Suárez, J., Quesada, C., Linnemann, U., D’lemos, R., Pisarevsky, S.A.,

Science 252 (5011), 1409–1412. 2007. Neoproterozoic-early Paleozoic paleogeography of the peri-Gondwanan

Hoskin, P.W.O., Black, L.P., 2000. Metamorphic zircon formation by solid-state terranes: Amazonian versus West African connections. In: Nasser, E., Lieˇıgeois,

recrystallization of protolith igneous zircon. Journal of Metamorphic Geology J.-P. (Eds.), The Boundaries of the West African Craton. Geological Society of

18 (4), 423–439. London, Special Publication, pp. 345–383.

M. Ibanez-Mejia et al. / Precambrian Research 191 (2011) 58–77 77

Nemchin, A., Cawood, P., 2005. Discordance of the U–Pb system in detrital zircons: Tassinari, C.C.G., et al., 1996. Geochronological systematics on basement rocks from

implication for provenance studies of sedimentary rocks. Sedimentary Geology the Rio Negro-Juruena province (Amazonian Craton), and tectonic implications.

182 (1–4), 143–162. International Geology Review 38 (2), 161–175.

Ordonez-Carmona, O., Pimentel, M.M., De Moraes, R., 2002. Granulitas de Los Man- Teixeira, W., Geraldes, M.C., Matos, R., Salina Ruiz, A., Saes, G., Vargas-Mattos, G.,

gos: un fragmento grenviliano en la parte SE de la Sierra Nevada de Santa Marta. 2010. A review of the tectonic evolution of the Sunsás belt, SW Amazonian

Revista de la Academia Colombiana de Ciencias Exactas, Fısicas y Naturales 26 Craton. Journal of South American Earth Sciences 29 (1), 47–60.

(99), 169–179. Teixeira, W., Tassinari, C., Cordani, U., Kawashita, K., 1989. A review of the

Ordonez-Carmona, O., Pimentel, M.M., De Moraes, R., Restrepo, J.J., 1999. Rocas geochronology of the Amazonian Craton – Tectonic implications. Precambrian

Grenvillianas en la region de Puerto Berrio – Antioquia. Revista de la Academia Research 42 (3–4), 213–227.

Colombiana de Ciencias Exactas, Físicas y Naturales 23 (87), 225–232. Tohver, E., Bettencourt, J.S., Tosdal, R., Mezger, K., Leite, W.B., Payolla, B.L., 2004a.

Ordonez-Carmona, O., Restrepo Alvarez, J.J., Pimentel, M.M., 2006. Geochronological Terrane transfer during the Grenville orogeny: tracing the Amazonian ances-

and isotopical review of pre-Devonian crustal basement of the Colombian Andes. try of southern Appalachian basement through Pb and Nd isotopes. Earth and

Journal of South American Earth Sciences 21 (4), 372–382. Planetary Science Letters 228 (1–2), 161–176.

Parra, M., et al., 2009. Orogenic wedge advance in the northern Andes: evidence Tohver, E., Van der Pluijm, B.A., Mezger, K., Essene, E., Scandorala, J.E., Rizzotto, G.J.,

from the Oligocene-Miocene sedimentary record of the Medina Basin, Eastern 2004b. Signiﬁcance of the Nova Brasilandia metasedimentary belt in western

Cordillera Colombia. Geological Society of America Bulletin 121 (5–6), 780–800. Brazil: redeﬁning the Mesoproterozoic boundary of the Amazon Craton. Tec-

Passchier, C.W., Trouw, R.A.J., 2005. Microtectonics. Springer-Verlag, Berlin, 366 pp. tonics 23 (6), TC6004.

Pisarevsky, S.A., Wingate, M.T.D., Powell, C.M., Johnson, S., Evans, D.A.D., 2003. Mod- Tohver, E., Teixeira, W., Van der Pluijm, B.A., Geraldes, M.C., Bettencourt, J.S., Rizzotto,

els of Rodinia assembly and fragmentation. Geological Society, London, Special G., 2006. Restored transect across the exhumed Grenville orogen of Lauren-

Publications 206 (1), 35–55. tia and Amazonia, with implications for crustal architecture. Geology 34 (8),

Priem, H.N.A., Andriessen, P., Boelrijk, N.A.I.M., De Boorder, H., Hebeda, E.H., Huguett, 669–672.

A., Verdurmen, E., Verschure, R., 1982. Geochronology of the Precambrian in the Tohver, E., van der Pluijm, B., Van der Voo, R., Rizzotto, G., Scandolara, J., 2002. Pale-

Amazonas region of southeastern Colombia (Western Guiana Shield). Geologie ogeography of the Amazon Craton at 1.2 Ga: early Grenvillian collision with

Mijnbouw 61 (3), 229–242. the Llano segment of Laurentia. Earth and Planetary Science Letters 199 (1–2),

Priem, H., Kroonenberg, S., Boelrijk, N., Hebeda, E., 1989. Rb–Sr and K–Ar evidence 185–200.

for the presence of a 1.6 Ga basement underlying the 1.2 Ga Garzón-Santa Marta Tollo, R.P., Aleinikoff, J.N., Borduas, E.A., Hackley, P.C., Fanning, C.M., 2004. Petro-

granulite belt in the Colombian Andes. Precambrian Research 42 (3–4), 315–324. logic and geochronologic evolution of the Grenville orogen, northern Blue Ridge

Proradam, 1979. La Amazonia Colombiana y sus recursos – Proyecto Radargramet- province, Virginia. Petrologic and geochronologic evolution of the Grenville

rico del Amazonas. Ingeominas, Bogota, 590 pp. orogen, northern Blue Ridge province Virginia. In: Tollo, R.P., Corriveau, L.,

Ramos, V.A., 2010. The Grenville-age basement of the Andes. Journal of South Amer- McLelland, J., Bartholomew, M.J. (Eds.), Proterozoic Tectonic Evolution of the

ican Earth Science 29 (1), 77–91. Grenville Orogen in North America. Geological Society of America Memoir No.

Reese, J., Mosher, S., 2004. Kinematic constraints on Rodinia reconstructions from 197, pp. 647–677.

the core of the Texas Grenville orogen. Journal of Geology 112 (2), 185–205. Toussaint, J.F., 1993. Precaˇımbrico–Paleozoˇıico. Evolucioˇın geoloˇıgica de Colombia.

Restrepo-Pace, P., Ruiz, J., Gehrels, G., Cosca, M., 1997. Geochronology and Nd iso- Universidad Nacional de Colombia, Medellin, p. 129.

topic data of Grenville-age rocks in the Colombian Andes: new constraints for Trumpy, D., 1943. Pre-Cretaceous of Colombia. Geological Society American Bulletin

late Proterozoic Early Paleozoic paleocontinental reconstructions of the Ameri- 54, 1281–1304.

cas. Earth and Planetary Science Letters 150 (3–4), 427–441. Tschanz, C., Richard, F.M., Cruz, B.J., Harald, H.M., Gerald, T.C., 1974. Geologic evo-

Rivers, T., 1997. Lithotectonic elements of the Grenville Province: review and tec- lution of the Sierra Nevada de Santa Marta, Northeastern Colombia. Geological

tonic implications. Precambrian Research 86 (3–4), 117–154. Society American Bulletin 85, 273–284.

Ruiz, J., Tosdal, R.M., Restrepo-Pace, P.A., Murillo-Mun˜eton, G. (Eds.), 1999. Pb Iso- Vasquez, M., Altenberger, U., Romer, R.L., 2009. Neogene magmatism and its possible

tope evidence for Colombian-southern Mexico connections in the Proterozoic. causal relationship with hydrocarbon generation in SW Colombia. International

Geological Society of America Special Paper, p. 336. Journal of Earth Science 98 (5), 1053–1062.

Sadowski, G., Bettencourt, J., 1996. Mesoproterozoic tectonic correlations between Vinasco, C.J., Cordani, U.G., González, H., Weber, M., Pelaez, C., 2006. Geochronolog-

eastern Laurentia and the western border of the Amazon Craton. Precambrian ical, isotopic, and geochemical data from Permo-Triassic granitic gneisses and

Research 76 (3–4), 213–227. granitoids of the Colombian Central Andes. Journal of South American Earth

Santos, J.O.S., Hartmann, L.A., Hartmann, L.A., Gaudette, H.E., Groves, D.I., Sciences 21, 355–371.

McNaughton, N.J., Fletcher, I.R., 2000. A new understanding of the provinces of Walker, N., 1992. Middle Proterozoic geologic evolution of Llano Uplift, Texas – evi-

the Amazon Craton based on integration of ﬁeld mapping and U–Pb and Sm–Nd dence from U–Pb zircon geochronometry. Geological Society American Bulletin

geochronology. Gondwana Research 3 (4), 453–488. 104 (4), 494–504.

Santos, J.O.S., Rizzotto, G.J., Potter, P.E., McNaughton, N.J., Matos, R.S., Hartmann, L.A., Weber, B., Hecht, L., 2003. Petrology and geochemistry of metaigneous rocks from

Chemale, F., Quadros, M.E.S., 2008. Age and autochthonous evolution of the Sun- a Grenvillian basement fragment in the Maya block: the Guichicovi complex,

sás Orogen in West Amazon Craton based on mapping and U–Pb geochronology. Oaxaca, southern Mexico. Precambrian Research 124 (1), 41–67.

Precambrian Research 165 (3–4), 120–152. Weber, B., Kohler, H., 1999. Sm-Nd, Rb–Sr and U–Pb geochronology of a Grenville ter-

Solari, L.A., Keppie, J.D., Ortega-Gutiérrez, F., Cameron, K.L., Lopez, R., Hames, W.E., rane in southern Mexico: origin and geologic history of the Guichicovi complex.

2003. 990 and 1100 Ma Grenvillian tectonothermal events in the northern Oax- Precambrian Research 96 (3–4), 245–262.

acan Complex, southern Mexico: roots of an orogen. Tectonophysics 365 (1–4), Weber, B., Valencia, V.A., Schaaf, P., Pompa-Mera, V., Ruiz, J., 2008. Signiﬁcance

257–282. of provenance ages from the Chiapas Massif complex (Southeastern Mexico):

Stacey, J.S., Kramers, J.D., 1975. Approximation of terrestrial lead isotope evolution redeﬁning the Paleozoic basement of the Maya block and its evolution in a

by a two-stage model. Earth and Planetary Science Letters 26, 207–221. peri-Gondwanan Realm. Journal of Geology 116 (6), 619–639.

Strachan, R.A., Collins, A.S., Buchan, C., Nance, R.D., Murphy, J.B., D’Lemos, R.S., 2007. Weber, B., Scherer, E.E., Schulze, C., Valencia, V.A., Montecinos, P., Mezger, K., Ruiz, J.,

Terrane analysis along a Neoproterozoic active margin of Gondwana: insights 2010. U–Pb and Lu–Hf isotope systematics of lower crust from central-southern

from U–Pb zircon geochronology. Journal of the Geological Society of London Mexico – geodynamic signiﬁcance of Oaxaquia in a Rodinia Realm. Precambrian

164 (1), 57–60. Research 182 (1–2), 149–162.

Tassinari, C., Macambira, M., 1999. Geochronological provinces of the Amazonian Whitney, D.L., Evans, B.W., 2010. Abbreviations for names of rock-forming minerals.

Craton. Episodes 22 (3), 174–182. American Mineralogist 95 (1), 185–187.